LMH6601MG [NSC]

250 MHz, 2.4V CMOS Op Amp with Shutdown; 250兆赫, 2.4V CMOS运算放大器,带有关断
LMH6601MG
型号: LMH6601MG
厂家: National Semiconductor    National Semiconductor
描述:

250 MHz, 2.4V CMOS Op Amp with Shutdown
250兆赫, 2.4V CMOS运算放大器,带有关断

运算放大器
文件: 总27页 (文件大小:1509K)
中文:  中文翻译
下载:  下载PDF数据表文档文件
June 2006  
LMH6601  
250 MHz, 2.4V CMOS Op Amp with Shutdown  
General Description  
Features  
The LMH6601 is a low voltage (2.4V – 5.5V), high speed  
voltage feedback operational amplifier suitable for use in a  
variety of consumer and industrial applications. With a band-  
width of 125 MHz at a gain of +2 and guaranteed high output  
current of 100 mA, the LMH6601 is an ideal choice for video  
line driver applications including HDTV. Low input bias cur-  
rent (50 pA maximum), rail-to-rail output, and low current  
noise allow the LMH6601 to be used in various industrial  
applications such as transimpedance amplifiers, active fil-  
ters, or high-impedance buffers. The LMH6601 is an attrac-  
tive solution for systems which require high performance at  
low supply voltages. The LMH6601 is available in a 6-pin  
SC70 package, and includes a micropower shutdown fea-  
ture.  
VS = 3.3V, TA = 25˚C, AV = 2 V/V, RL = 150to V, unless  
specified.  
n 125 MHz −3 dB small signal bandwidth  
n 75 MHz −3 dB large signal bandwidth  
n 30 MHz large signal 0.1 dB gain flatness  
n 260 V/µs slew rate  
n 0.25%/0.25˚ differential gain/differential phase  
n Rail-to-rail output  
n 2.4V – 5.5V single supply operating range  
n SC70-6 Package  
Applications  
n Video amplifier  
n Charge amplifier  
n Set-top box  
n Sample & hold  
n Transimpedance amplifier  
n Line driver  
n High impedance buffer  
Response at a Gain of +2 for Various Supply Voltages  
20136441  
© 2006 National Semiconductor Corporation  
DS201364  
www.national.com  
Absolute Maximum Ratings (Note 1)  
Storage Temperature Range  
Junction Temperature  
−65˚C to +150˚C  
+150˚C  
If Military/Aerospace specified devices are required,  
please contact the National Semiconductor Sales Office/  
Distributors for availability and specifications.  
Soldering Information  
Infrared or Convection (20 sec.)  
Wave Soldering (10 sec.)  
235˚C  
260˚C  
ESD Tolerance (Note 4)  
Human Body Model  
Machine Model  
2 kV  
200V  
2.5V  
Operating Ratings (Note 1)  
Supply Voltage (V+ – V)  
VIN Differential  
2.4V to 5.5V  
Input Current  
10 mA  
Operating Temperature Range  
−40˚C to +85˚C  
Output Current  
200 mA (Note 3)  
Package Thermal Resistance (θJA  
)
Supply Voltage (V+ – V)  
6.0V  
6-pin SC70  
414˚C/W  
Voltage at Input/Output Pins  
V++0.5V, V−0.5V  
5V Electrical Characteristics Single Supply with VS= 5V, AV = +2, RF = 604, SD tied to V+, VOUT  
=
VS/2, RL = 150to Vunless otherwise specified. Boldface limits apply at temperature extremes. (Note 2)  
Symbol  
Parameter  
Condition  
Min  
Typ  
Max  
Units  
(Note 6) (Note 6) (Note 6)  
Frequency Domain Response  
SSBW  
SSBW_1  
Peak  
–3 dB Bandwidth Small Signal VOUT = 0.25 VPP  
130  
250  
2.5  
0
MHz  
VOUT = 0.25 VPP, AV = +1  
VOUT = 0.25 VPP, AV = +1  
VOUT = 0.25 VPP  
Peaking  
Peaking  
dB  
dB  
Peak_1  
LSBW  
–3 dB Bandwidth Large Signal VOUT = 2 VPP  
81  
MHz  
dB  
Peak_2  
Peaking  
VOUT = 2 VPP  
0
0.1 dB BW 0.1 dB Bandwidth  
VOUT = 2 VPP  
30  
MHz  
GBWP_1k  
GBWP_150  
AVOL  
Gain Bandwidth Product  
Unity Gain, RL = 1 kto VS/2  
Unity Gain, RL = 150to VS/2  
155  
125  
MHz  
<
<
Large Signal Open Loop Gain 0.5V VOUT 4.5V  
56  
66  
30  
dB  
PBW  
Full Power BW  
Differential Gain  
Differential Phase  
–1 dB, AV = +4, VOUT = 4.2 VPP  
,
MHz  
RL = 150to VS/2  
DG  
DP  
4.43 MHz, 1.7V VOUT 3.3V,  
RL = 150to V−  
0.06  
0.10  
%
4.43 MHz, 1.7V VOUT 3.3V  
RL = 150to V−  
deg  
Time Domain Response  
TRS/TRL  
OS  
Rise & Fall Time  
0.25V Step  
2.6  
10  
ns  
%
Overshoot  
Slew Rate  
Settling Time  
0.25V Step  
SR  
2V Step  
275  
50  
V/µs  
TS  
1V Step, 0.1%  
1V Step, 0.02%  
ns  
TS_1  
PD  
220  
2.4  
50  
Propagation Delay  
Input to Output, 250 mV Step, 50%  
AV = −1, 10% Overshoot, 75in  
Series  
ns  
CL  
Cap Load Tolerance  
pF  
Distortion & Noise Performance  
HD2  
HD2_1  
HD3  
HD3_1  
THD  
VN1  
Harmonic Distortion (2nd  
)
2 VPP, 10 MHz  
−56  
−61  
−73  
−64  
−58  
7
dBc  
dBc  
4 VPP, 10 MHz, RL = 1 kto VS/2  
2 VPP, 10 MHz  
Harmonic Distortion (3rd)  
4 VPP, 10 MHz, RL = 1 kto VS/2  
4 VPP, 10 MHz, RL = 1 kto VS/2  
Total Harmonic Distortion  
Input Voltage Noise  
>
10 MHz  
nV/  
fA/  
VN2  
1 MHz  
10  
>
IN  
Input Current Noise  
1 MHz  
50  
www.national.com  
2
5V Electrical Characteristics Single Supply with VS= 5V, AV = +2, RF = 604, SD tied to V+, VOUT = VS/2,  
RL = 150to Vunless otherwise specified. Boldface limits apply at temperature extremes. (Note 2) (Continued)  
Symbol  
Parameter  
Condition  
Min  
Typ  
Max  
Units  
(Note 6) (Note 6) (Note 6)  
Static, DC Performance  
VIO  
Input Offset Voltage  
1
2.4  
mV  
5.0  
DVIO  
Input Offset Voltage Average  
Drift  
(Note 8)  
−5  
µV/˚C  
IB  
Input Bias Current  
Input Offset Current  
Input Resistance  
Input Capacitance  
Positive Power Supply  
Rejection Ratio  
(Note 9)  
(Note 9)  
5
2
50  
25  
pA  
pA  
GΩ  
pF  
IOS  
>
RIN  
100  
1.3  
59  
CIN  
+PSRR  
DC  
DC  
55  
51  
dB  
−PSRR  
CMRR  
Negative Power Supply  
Rejection Ratio  
53  
61  
68  
dB  
dB  
50  
Common Mode Rejection Ratio DC  
56  
53  
V-0.20  
>
CMVR  
ICC  
Input Voltage Range  
Supply Current  
CMRR 50 dB  
Normal Operation  
VOUT = VS/2  
V+ - 1.5  
11.5  
V
9.6  
mA  
nA  
13.5  
Shutdown  
100  
SD tied to 0.5V (Note 5)  
RL = 150to V–  
VOH1  
Output High Voltage  
(Relative to V+)  
–210  
–190  
–480  
VOH2  
VOH3  
RL = 75to VS/2  
RL = 10 kto V–  
–190  
–12  
mV  
mV  
–60  
–110  
VOL1  
Output Low Voltage  
(Relative to V)  
RL = 150to V–  
+5  
+45  
+125  
VOL2  
VOL3  
RL = 75to VS/2  
RL = 10 kto V–  
+120  
+5  
+45  
+125  
<
IO  
Output Current  
VOUT 0.6V from  
Source  
Sink  
150  
180  
Respective Supply  
mA  
IO_1  
Load  
VOUT = VS/2,  
100  
VID  
=
18 mV (Note 10)  
<
Output Load Rating  
THD −30 dBc, f = 200 kHz,  
RL tied to VS/2, VOUT = 4 VPP  
Enabled, AV = +1  
20  
RO_Enabled Output Resistance  
RO_Disabled Output Resistance  
CO_Disabled Output Capacitance  
Miscellaneous Performance  
0.2  
>
Shutdown  
100  
MΩ  
pF  
Shutdown  
5.0  
VDMAX  
VDMIN  
Ii  
Voltage Limit for Disable (Pin 5) (Note 5)  
Voltage Limit for Enable (Pin 5) (Note 5)  
0
0.5  
5.0  
V
V
4.5  
Logic Input Current (Pin 5)  
Turn-on Glitch  
SD = 5V (Note 5)  
10  
2.2  
1.4  
520  
60  
pA  
V
V_glitch  
Ton  
Turn-on Time  
µs  
ns  
dB  
ns  
Toff  
Turn-off Time  
IsolationOFF Off Isolation  
T_OL Overload Recovery  
1 MHz, RL = 1 kΩ  
<
20  
3
www.national.com  
3.3V Electrical Characteristics Single Supply with VS= 3.3V, AV = +2, RF = 604, SD tied to V+,  
VOUT = VS/2, RL = 150to Vunless otherwise specified. Boldface limits apply at temperature extremes. (Note 2)  
Symbol  
Parameter  
Condition  
Min  
Typ  
Max  
Units  
(Note 6) (Note 6) (Note 6)  
Frequency Domain Response  
SSBW  
SSBW_1  
Peak  
–3 dB Bandwidth Small Signal VOUT = 0.25 VPP  
125  
250  
3
MHz  
VOUT = 0.25 VPP, AV = +1  
VOUT = 0.25 VPP, AV = +1  
VOUT = 0.25 VPP  
Peaking  
Peaking  
dB  
dB  
Peak_1  
LSBW  
0.05  
75  
–3 dB Bandwidth Large Signal VOUT = 2 V  
MHz  
dB  
PP  
Peak_2  
Peaking  
VOUT = 2 VPP  
0
0.1 dB BW 0.1 dB Bandwidth  
VOUT = 2 VPP  
30  
MHz  
GBWP_1k  
GBWP_150  
AVOL  
Gain Bandwidth Product  
Unity Gain, RL = 1 kto VS/2  
Unity Gain, RL = 150to VS/2  
115  
105  
MHz  
<
<
Large Signal Open Loop Gain 0.3V VOUT 3V  
56  
67  
30  
dB  
PBW  
Full Power BW  
Differential Gain  
Differential Phase  
–1 dB, AV = +4, VOUT = 2.8VPP  
,
MHz  
RL = 150to VS/2  
DG  
DP  
4.43 MHz, 0.85V VOUT 2.45V,  
RL = 150to V−  
0.0.6  
0.23  
%
4.43 MHz, 0.85V VOUT 2.45V  
RL = 150to V−  
deg  
Time Domain Response  
TRS/TRL  
OS  
Rise & Fall Time  
0.25V Step  
2.7  
10  
ns  
%
Overshoot  
Slew Rate  
Settling Time  
0.25V Step  
SR  
2V Step  
260  
70  
V/µs  
TS  
1V Step, 0.1%  
1V Step, 0.02%  
Input to Output, 250 mV Step, 50%  
AV = −1, 10% Overshoot, 82in  
Series  
ns  
TS_1  
PD  
300  
2.6  
50  
Propagation Delay  
ns  
CL  
Cap Load Tolerance  
pF  
Distortion & Noise Performance  
HD2  
Harmonic Distortion (2nd  
)
2 VPP, 10 MHz  
2 VPP, 10 MHz  
RL = 1 kto VS/2  
2 VPP, 10 MHz  
2 VPP, 10 MHz  
RL = 1 kto VS/2  
2 VPP, 10 MHz  
RL = 1 kto VS/2  
−61  
−79  
dBc  
HD2_1  
HD3  
Harmonic Distortion (3rd)  
−53  
−69  
dBc  
dBc  
HD3_2  
THD  
Total Harmonic Distortion  
Input Voltage Noise  
Input Current Noise  
−66  
>
VN1  
VN2  
IN  
10 MHz  
7
nV/  
fA/  
mV  
1 MHz  
10  
50  
>
1 MHz  
Static, DC Performance  
VIO  
Input Offset Voltage  
1
2.6  
5.5  
DVIO  
Input Offset Voltage Average  
Drift  
(Note 8)  
−4.5  
µV/˚C  
IB  
Input Bias Current  
Input Offset Current  
Input Resistance  
Input Capacitance  
(Note 9)  
(Note 9)  
5
2
50  
25  
pA  
pA  
GΩ  
pF  
IOS  
RIN  
CIN  
>
100  
1.4  
www.national.com  
4
3.3V Electrical Characteristics Single Supply with VS= 3.3V, AV = +2, RF = 604, SD tied to V+,  
VOUT = VS/2, RL = 150to Vunless otherwise specified. Boldface limits apply at temperature extremes. (Note  
2) (Continued)  
Symbol  
+PSRR  
Parameter  
Condition  
Min  
Typ  
Max  
Units  
dB  
(Note 6) (Note 6) (Note 6)  
Positive Power Supply  
Rejection Ratio  
DC  
DC  
61  
51  
80  
72  
73  
−PSRR  
CMRR  
Negative Power Supply  
Rejection Ratio  
57  
dB  
52  
Common Mode Rejection Ratio DC  
58  
dB  
55  
V-0.20  
>
CMVR  
ICC  
Input Voltage Range  
Supply Current  
CMRR 50 dB  
Normal Operation  
VOUT = VS/2  
V+ -1.5  
11  
V
9.2  
mA  
nA  
13  
Shutdown  
100  
SD tied to 0.33V (Note 5)  
RL = 150to V–  
VOH1  
Output High Voltage  
(Relative to V+)  
–210  
–190  
–360  
VOH2  
VOH3  
RL = 75to VS/2  
RL = 10 kto V−  
–190  
–10  
mV  
mV  
–50  
–100  
VOL1  
Output Low Voltage  
(Relative to V)  
RL = 150to V–  
+4  
+45  
+125  
VOL2  
VOL3  
RL = 75to VS/2  
RL = 10 kto V–  
+105  
+4  
+45  
+125  
<
IO  
Output Current  
VOUT 0.6V from  
Source  
Sink  
50  
75  
Respective Supply  
mA  
IO_1  
Load  
VOUT = VS/2, VID  
(Note 10)  
=
18 mV  
75  
<
Output Load Rating  
THD −30 dBc, f = 200 kHz,  
RL tied to VS/2, VOUT = 2.6 VPP  
Enabled, AV = +1  
25  
RO_Enabled Output Resistance  
RO_Disabled Output Resistance  
CO_Disabled Output Capacitance  
Miscellaneous Performance  
0.2  
>
Shutdown  
100  
MΩ  
pF  
Shutdown  
5.6  
VDMAX  
VDMIN  
Ii  
Voltage Limit for Disable (Pin 5) (Note 5)  
Voltage Limit for Enable (Pin 5) (Note 5)  
0
0.33  
3.3  
V
V
2.97  
Logic Input Current (Pin 5)  
Turn-on Glitch  
SD = 3.3V (Note 5)  
8
pA  
V
V_glitch  
Ton  
1.6  
3.5  
500  
60  
Turn-on Time  
µs  
ns  
dB  
Toff  
Turn-off Time  
IsolationOFF Off Isolation  
1 MHz, RL = 1 kΩ  
5
www.national.com  
2.7V Electrical Characteristics Single Supply with VS = 2.7V, AV = +2, RF = 604, SD tied to V+, VOUT  
= VS/2, RL = 150to Vunless otherwise specified. Boldface limits apply at temperature extremes. (Note 2)  
Symbol  
Parameter  
Condition  
Min  
Typ  
Max  
Units  
(Note 6) (Note 6) (Note 6)  
Frequency Domain Response  
SSBW  
SSBW_1  
Peak  
–3 dB Bandwidth Small Signal VOUT = 0.25 VPP  
120  
250  
3.1  
0.1  
73  
MHz  
VOUT = 0.25 VPP, AV = +1  
VOUT = 0.25 VPP, AV = +1  
VOUT = 0.25 VPP  
Peaking  
Peaking  
dB  
dB  
Peak_1  
LSBW  
–3 dB Bandwidth Large Signal VOUT = 2 V  
MHz  
dB  
PP  
Peak_2  
Peaking  
VOUT = 2 VPP  
0
0.1 dB BW 0.1 dB Bandwidth  
VOUT = 2VPP  
30  
MHz  
GBWP_1k  
GBWP_150  
AVOL  
Gain Bandwidth Product  
Unity Gain, RL = 1 kto VS/2  
Unity Gain, RL = 150to VS/2  
110  
81  
MHz  
<
<
Large Signal Open Loop Gain 0.25V VOUT 2.5V  
56  
65  
13  
dB  
PBW  
Full Power BW  
Differential Gain  
Differential Phase  
–1 dB, AV = +4, VOUT = 2 VPP  
RL = 150to VS/2  
,
MHz  
DG  
DP  
4.43 MHz, 0.45V VOUT 2.05V  
RL = 150to V−  
0.12  
0.62  
%
4.43 MHz, 0.45V VOUT 2.05V  
RL = 150to V−  
deg  
Time Domain Response  
TRS/TRL  
OS  
Rise & Fall Time  
0.25V Step  
2.7  
10  
ns  
%
Overshoot  
Slew Rate  
Settling Time  
0.25V Step  
SR  
2V Step  
260  
147  
410  
3.4  
V/µs  
TS  
1V Step, 0.1%  
1V Step, 0.02%  
Input to Output, 250 mV Step, 50%  
ns  
ns  
TS_1  
PD  
Propagation Delay  
Distortion & Noise Performance  
HD2  
HD3  
VN1  
VN2  
IN  
Harmonic Distortion (2nd  
Harmonic Distortion (3rd)  
)
1 VPP, 10 MHz  
1 VPP, 10 MHz  
−58  
−60  
8.4  
12  
dBc  
dBc  
>
Input Voltage Noise  
10 MHz  
1 MHz  
nV/  
fA/  
>
Input Current Noise  
1 MHz  
50  
Static, DC Performance  
VIO  
Input Offset Voltage  
1
3.5  
mV  
6.5  
DVIO  
Input Offset Voltage Average  
Drift  
(Note 8)  
−6.5  
µV/˚C  
IB  
Input Bias Current  
Input Offset Current  
Input Resistance  
Input Capacitance  
Positive Power Supply  
Rejection Ratio  
(Note 9)  
(Note 9)  
5
2
50  
pA  
pA  
GΩ  
pF  
IOS  
25  
>
RIN  
100  
1.6  
68  
CIN  
+PSRR  
DC  
DC  
58  
53  
dB  
−PSRR  
CMRR  
CMVR  
Negative Power Supply  
Rejection Ratio  
56  
69  
77  
dB  
dB  
53  
Common Mode Rejection Ratio DC  
Input Voltage Range CMRR 50 dB  
57  
52  
V-0.20  
V+ -1.5  
V
>
www.national.com  
6
2.7V Electrical Characteristics Single Supply with VS = 2.7V, AV = +2, RF = 604, SD tied to V+, VOUT  
=
VS/2, RL = 150to Vunless otherwise specified. Boldface limits apply at temperature extremes. (Note 2) (Continued)  
Symbol  
ICC  
Parameter  
Supply Current  
Condition  
Min  
Typ  
Max  
Units  
(Note 6) (Note 6) (Note 6)  
Normal Operation  
9.0  
100  
10.6  
mA  
nA  
VOUT = VS/2  
12.5  
Shutdown  
SD tied to 0.27V (Note 5)  
RL = 150to V–  
VOH1  
Output High Voltage  
(Relative to V+)  
–260  
–200  
–420  
VOH2  
VOH3  
RL = 75to VS/2  
RL = 10 kto V–  
–200  
–10  
mV  
mV  
–50  
100  
VOL1  
Output Low Voltage  
(Relative to V)  
RL = 150to V–  
+4  
+45  
+125  
VOL2  
VOL3  
RL = 75to VS/2  
RL = 10 kto V–  
+125  
+4  
+45  
125  
IO  
Output Current  
VOUT 0.6V from  
Respective Supply  
Source  
Sink  
25  
62  
mA  
IO_1  
Load  
VOUT = VS/2, VID  
mV (Note 10)  
=
18  
Source  
Sink  
25  
35  
<
Output Load Rating  
THD −30 dBc, f = 200 kHz, RL tied  
to VS/2, VOUT = 2.2 VPP  
Enabled, AV = +1  
40  
RO_Enable Output Resistance  
RO_Disabled Output Resistance  
CO_Disabled Output Capacitance  
Miscellaneous Performance  
0.2  
>
Shutdown  
100  
MΩ  
pF  
Shutdown  
5.6  
VDMAX  
VDMIN  
Ii  
Voltage Limit for Disable (Pin 5) (Note 5)  
Voltage Limit for Enable (Pin 5) (Note 5)  
0
0.27  
2.7  
V
V
2.43  
Logic Input Current (Pin 5)  
Turn-on Glitch  
SD = 2.7V (Note 5)  
4
pA  
V
V_glitch  
Ton  
1.2  
5.2  
760  
60  
Turn-on Time  
µs  
ns  
dB  
Toff  
Turn-off Time  
IsolationOFF Off Isolation  
1 MHz, RL = 1 kΩ  
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is  
intended to be functional, but specific performance is not guaranteed. For guaranteed specifications and the test conditions, see the Electrical Characteristics.  
Note 2: Electrical Table values apply only for factory testing conditions at the temperature indicated. Factory testing conditions result in very limited self-heating of  
>
the device such that T = T . No guarantee of parametric performance is indicated in the electrical tables under conditions of internal self-heating where T  
T .  
J
A
J
A
Note 3: The maximum continuous output current (I  
) is determined by device power dissipation limitations.  
OUT  
Note 4: Human Body Model is 1.5 kin series with 100 pF. Machine Model is 0in series with 200 pF.  
Note 5: SD logic is CMOS compatible. To ensure proper logic level and to minimize power supply current, SD should typically be less than 10% of total supply  
voltage away from either supply rail.  
Note 6: Typical numbers are the most likely parametric norm. Bold numbers refer to over temperature limits.  
Note 7: Negative input current implies current flowing out of the device.  
Note 8: Drift determined by dividing the change in parameter at temperature extremes by the total temperature change.  
Note 9: Guaranteed by design.  
Note 10: “V ” is input differential voltage (input overdrive).  
ID  
7
www.national.com  
Connection Diagram  
6-Pin SC70  
20136401  
Top View  
Ordering Information  
Package  
Part Number  
LMH6601MG  
LMH6601MGX  
Package Marking  
Transport Media  
NSC Drawing  
1k Units Tape and Reel  
3k Units Tape and Reel  
6-Pin SC70  
A95  
MAA06A  
www.national.com  
8
Typical Performance Characteristics Unless otherwise noted, all data is with AV = +2, RF = RG  
=
604, VS = 3.3V, VOUT = VS/2, SD tied to V+, RL = 150to V, T = 25˚C.  
Frequency Response for Various Output Amplitudes  
Frequency Response for Various Output Amplitudes  
20136414  
20136413  
Frequency Response for Various Output Amplitudes  
−3 dB BW vs. Supply Voltage for Various Output Swings  
20136420  
20136415  
Non-inverting Frequency Response for Various Gain  
Inverting Frequency Response for Various Gain  
20136416  
20136417  
9
www.national.com  
Typical Performance Characteristics Unless otherwise noted, all data is with AV = +2, RF = RG  
=
604, VS = 3.3V, VOUT = VS/2, SD tied to V+, RL = 150to V, T = 25˚C. (Continued)  
Frequency Response for Various Loads  
Frequency Response for Various Supply Voltages  
20136419  
20136421  
−3 dB BW vs. Ambient Temperature  
Frequency Response for Various Cap Load  
20136422  
20136418  
Frequency Response for Various Supply Voltage  
Max Output Swing vs. Frequency  
20136426  
20136441  
www.national.com  
10  
Typical Performance Characteristics Unless otherwise noted, all data is with AV = +2, RF = RG  
=
604, VS = 3.3V, VOUT = VS/2, SD tied to V+, RL = 150to V, T = 25˚C. (Continued)  
Output Swing vs. Sink Current for Various Supply  
Voltages  
Peak Output Swing vs. RL  
20136427  
20136464  
Output Swing vs. Source Current for Various Supply  
Voltages  
HD2 vs. Frequency  
20136404  
20136465  
HD3 vs. Frequency  
THD vs. Output Swing  
20136405  
20136402  
11  
www.national.com  
Typical Performance Characteristics Unless otherwise noted, all data is with AV = +2, RF = RG  
=
604, VS = 3.3V, VOUT = VS/2, SD tied to V+, RL = 150to V, T = 25˚C. (Continued)  
THD vs. Output Swing  
Slew Rate vs. Ambient Temperature  
20136423  
20136403  
Settling Time ( 1%) vs. Output Swing  
Output Settling  
20136412  
20136411  
Isolation Resistor & Settling Time vs. CL  
Isolation Resistor & Settling Time vs. CL  
20136429  
20136428  
www.national.com  
12  
Typical Performance Characteristics Unless otherwise noted, all data is with AV = +2, RF = RG  
=
604, VS = 3.3V, VOUT = VS/2, SD tied to V+, RL = 150to V, T = 25˚C. (Continued)  
Closed Loop Output Impedance vs. Frequency for  
Various Supply Voltages  
Off Isolation vs. Frequency  
20136410  
20136408  
Noise Voltage vs. Frequency  
Open Loop Gain/ Phase  
20136435  
20136424  
CMRR vs. Frequency  
+PSRR vs. Frequency  
20136425  
20136439  
13  
www.national.com  
Typical Performance Characteristics Unless otherwise noted, all data is with AV = +2, RF = RG  
=
604, VS = 3.3V, VOUT = VS/2, SD tied to V+, RL = 150to V, T = 25˚C. (Continued)  
−PSRR vs. Frequency  
Supply Current vs. Ambient Temperature  
20136433  
20136440  
Supply Current vs. VCM  
Supply Current vs. Supply Voltage  
20136437  
20136467  
Offset Voltage vs. Ambient Temperature  
for 3 Representative Units  
Offset Voltage Distribution  
20136434  
20136436  
www.national.com  
14  
Typical Performance Characteristics Unless otherwise noted, all data is with AV = +2, RF = RG  
=
604, VS = 3.3V, VOUT = VS/2, SD tied to V+, RL = 150to V, T = 25˚C. (Continued)  
Offset Voltage vs. VCM (Typical Part)  
Input Bias Current vs. Common Mode Voltage  
20136438  
20136442  
Small Signal Step Response  
Large Signal Step Response  
20136430  
20136431  
Large Signal Step Response  
Turn On/Off Waveform  
20136466  
20136432  
15  
www.national.com  
Typical Performance Characteristics Unless otherwise noted, all data is with AV = +2, RF = RG  
=
604, VS = 3.3V, VOUT = VS/2, SD tied to V+, RL = 150to V, T = 25˚C. (Continued)  
DG vs. VOUT for Various VS  
DP vs. VOUT for Various VS  
20136472  
20136471  
DG vs. VOUT (DC and AC Coupled Load Compared)  
DP vs. VOUT (DC and AC Coupled Load Compared)  
20136473  
20136474  
www.national.com  
16  
Application Information  
OPTIMIZING PERFORMANCE  
With many op amps, additional device non-linearity and  
sometimes less loop stability arises when the output has to  
switch from current-source mode to current-sink mode or  
vice versa. When it comes to achieving the lowest distortion  
and the best Differential Gain/ Differential Phase (DG/ DP,  
broadcast video specs), the LMH6601 is optimized for single  
supply DC coupled output applications where the load cur-  
rent is returned to the negative rail (V). That is where the  
output stage is most linear (lowest distortion) and which  
corresponds to unipolar current flowing out of this device. To  
that effect, it is easy to see that the distortion specifications  
improve when the output is only sourcing current which is the  
distortion-optimized mode of operation for the LMH6601. In  
application where the LMH6601 output is AC coupled or  
when it is powered by separate dual supplies for V+ and V,  
the output stage supplies both source and sink current to the  
load and results in less than optimum distortion (and DG/  
DP). Figure 1 compares the distortion results between a DC  
and an AC coupled load to show the magnitude of this  
difference. See the DG/DP plots in the Typical Performance  
Characteristics section for a comparison between DC and  
AC coupling of the video load.  
20136470  
FIGURE 2. Output Pull-Down Value for Dual Supply &  
AC Coupling  
Furthermore, with a combination of low closed loop gain  
setting (i.e. AV = +1 for example where device bandwidth is  
>
the highest), light output loading (RL  
1 k) , and with a  
>
significant capacitive load (CL  
10 pF) , the LMH6601 is  
most stable if output sink current is kept to less than about 5  
mA. The pull-down method described in Figure 2 is appli-  
cable in these cases as well where the current that would  
normally be sunk by the op amp is diverted to the RP path  
instead.  
SHUTDOWN CAPABILITY AND TURN ON/ OFF  
BEHAVIOR  
With the device in shutdown mode, the output goes into high  
>
impedance (ROUT 100 M) mode. In this mode, the only  
path between the inputs and the output pin is through the  
external components around the device. So, for applications  
where there is active signal connection to the inverting input,  
with the LMH6601 in shutdown, the output could show signal  
swings due to current flow through these external compo-  
nents. For non-inverting amplifiers in shutdown, no output  
swings would occur, because of complete input-output iso-  
lation, with the exception of capacitive coupling.  
20136406  
FIGURE 1. Distortion Comparison between DC & AC  
Coupling of the Load  
For maximum power saving, the LMH6601 supply current  
drops to around 0.1 µA in shutdown. All significant power  
consumption within the device is disabled for this purpose.  
Because of this, the LMH6601 turn on time is measured in  
micro-seconds whereas its turn off is fast (nano-seconds) as  
would be expected from a high speed device like this.  
In certain applications, it may be possible to optimize the  
LMH6601 for best distortion (and DG/DP) even though the  
load may require bipolar output current by adding a pull-  
down resistor to the output. Adding an output pull-down  
resistance of appropriate value could change the LMH6601  
output loading into source-only. This comes at the price of  
higher total power dissipation and increased output current  
requirement.  
The LMH6601 SD pin is a CMOS compatible input with a  
pico-ampere range input current drive requirement. This pin  
needs to be tied to a level or otherwise the device state  
would be indeterminate. The device shutdown threshold is  
half way between the V+ and Vpin potentials at any supply  
voltage. For example, with V+ tied to 10V and Vequal to 5V,  
you can expect the threshold to be at 7.5V. The state of the  
device (shutdown or normal operation) is guaranteed over  
temperature as longs as the SD pin is held to within 10% of  
the total supply voltage.  
Figure 2 shows how to calculate the pull-down resistor value  
for both the dual supply and for the AC coupled load appli-  
cations.  
For V+ = 10V, V= 5V, as an example:  
Shutdown Range  
5V SD 5.5V  
9.5V SD 10V  
Normal Operation Range  
17  
www.national.com  
With some op amps, when the output approaches either one  
or both rails and saturation starts to set in, there is significant  
increase in the transistor parasitic capacitances which leads  
to loss of Phase Margin. That is why with these devices,  
there are sometimes hints of instability with output close to  
the rails. With the LMH6601, as can be seen in Figure 4, the  
output waveform remains free of instability throughout its  
range of voltages.  
Application Information (Continued)  
OVERLOAD RECOVERY AND SWING CLOSE TO RAILS  
The LMH6601 can recover from an output overload in less  
than 20 ns. See Figure 3 below for the input and output  
scope photos:  
SINGLE SUPPLY VIDEO APPLICATION  
The LMH6601’s high speed and fast slew rate make it an  
ideal choice for video amplifier and buffering applications.  
There are cost benefits in having a single operating supply.  
Single supply video systems can take advantage of the  
LMH6601’s low supply voltage operation along with its ability  
to operate with input common mode voltages at or slightly  
below the Vrail. Additional cost savings can be achieved by  
eliminating or reducing the value of the input and output AC  
coupling capacitors commonly employed in single supply  
video applications. This Application section shows some  
circuit techniques used to help in doing just that.  
DC COUPLED, SINGLE SUPPLY BASEBAND VIDEO  
AMPLIFIER/DRIVER  
20136407  
The LMH6601 output can swing very close to either rail to  
maximize the output dynamic range which is of particular  
interest when operating in a low voltage single supply envi-  
ronment. Under light output load conditions, the output can  
swing as close as a few milli-volts of either rail. This also  
allows a video amplifier to preserve the video black level for  
excellent video integrity. In the example shown below in  
Figure 5, the baseband video output is amplified and buff-  
ered by the LMH6601 which then drives the 75back ter-  
minated video cable for an overall gain of +1 delivered to the  
75load. The input video would normally have a level  
between 0V to approximately 0.75V.  
FIGURE 3. LMH6601 Output Overload Recovery  
Waveform  
In Figure 3, the input step function is set so that the output is  
driven to one rail and then the other and then the output  
recovery is measured from the time the input crosses 0V to  
when the output reaches this point.  
Also, when the LMH6601 input voltage range is exceeded  
near the V+ rail, the output does not experience output phase  
reversal, as some op amps do. This is particularly advanta-  
geous in applications where output phase reversal has to be  
avoided at all costs, such as in servo loop control among  
others. This adds to the LMH6601’s set of features which  
make this device easy to use.  
In addition, the LMH6601’s output swing close to either rail is  
well-behaved as can be seen in the scope photo of Figure 4.  
20136444  
FIGURE 5. Single Supply Video Driver Capable of  
Maintaining Accurate Video Black Level  
20136443  
FIGURE 4. LMH6601’s “Clean” Swing to Either Rail  
www.national.com  
18  
Application Information (Continued)  
With the LMH6601 input common mode range including the  
V(ground) rail, there will be no need for AC coupling or  
level shifting and the input can directly drive the non-  
inverting input which has the additional advantage of high  
amplifier input impedance. With LMH6601’s wide rail-to-rail  
output swing, as stated earlier, the video black level of 0V is  
maintained at the load with minimal circuit complexity and  
using no AC coupling capacitors. Without true rail-to-rail  
output swing of the LMH6601, and more importantly without  
the LMH6601’s ability of exceedingly close swing to V, the  
circuit would not operate properly as shown at the expense  
of more complexity. This circuit will also work for higher input  
voltages. The only significant requirement is that there is at  
least 1.8V from the maximum input voltage to the positive  
supply (V+).  
20136446  
FIGURE 7. Single Supply DC Coupled Composite  
The Composite Video Output of some low cost consumer  
video equipment consists of a current source which devel-  
ops the video waveform across a load resistor (usually 75),  
as shown in Figure 6 below. With these applications, the  
same circuit configuration just described and shown in Fig-  
ure 6 will be able to buffer and drive the Composite Video  
waveform which includes sync and video combined. How-  
ever, with this arrangement, the LMH6601 supply voltage  
needs to be at least 3.3V or higher in order to allow proper  
input common mode voltage headroom because the input  
can be as high as 1V peak.  
Video Driver for Negative Going Sync Tip  
In the circuit of Figure 7, the input is shifted positive by  
means of R1, R2, and RT in order to satisfy U1’s Common  
Mode input range. The signal will loose 20% of its amplitude  
in the process. The closed loop gain of U1 will need to be set  
to make up for this 20% loss in amplitude. This gives rise to  
the gain expression shown below which is based on a get-  
ting a 2 VPP output with a 0.8 VPP input:  
(1)  
R3 will produce a negative shift at the output due to VS (3.3V  
in this case). R3 will need to be set so that the “Video In” sync  
tip (−0.3V at RT or 0.61V at U1 non-inverting input) corre-  
sponds to near 0V at the output.  
(2)  
Equation (1) and Equation (2) need to be solved simulta-  
neously to arrive at the values of R3, RF, and RG which will  
satisfy both. From the datasheet, one can set RF = 620to  
be close to the recommended value for a gain of +2. It is  
easier to solve for RG and R3 by starting with a good esti-  
mate for one and iteratively solving Equation and Equation  
(2) to arrive at the results. Here is one possible iteration  
cycle for reference:  
20136445  
FIGURE 6. Single Supply Composite Video Driver for  
Consumer Video Outputs  
If the “Video In” signal is Composite Video with negative  
going Sync tip, a variation of the previous configurations  
should be used. This circuit produces a unipolar (above 0V)  
DC coupled single supply video signal as shown in Figure 7.  
19  
www.national.com  
RF = 620Ω  
TABLE 1. Finding Figure 7 External Resistor Values by Iteration  
Application Information (Continued)  
Estimate  
Calculated  
Equation (1) LHS  
Comment  
RG ()  
(from Equation (2))  
Calculated  
(Compare Equation (1) LHS Calculated to  
RHS)  
R3 ()  
1.69k  
1.56k  
1.37k  
239  
1k  
0.988  
1.15  
1.45  
4.18  
1.59  
Increase Equation (1) LHS by reducing RG  
Increase Equation (1) LHS by reducing RG  
Increase Equation (1) LHS by reducing RG  
Reduce Equation (1) LHS by increasing RG  
Close to target value of 1.5V/V for Equation (1)  
820  
620  
390  
560  
1.30k  
The final set of values for RG and R3 in Table 1 are values  
which will result in the proper gain and correct video levels  
(0V to 1V) at the output (VLOAD).  
Because of the DC bias at the output, the load needs to be  
AC coupled as well through CO. Some applications imple-  
ment a small valued ceramic capacitor (not shown) in paral-  
lel with CO which is electrolytic. The reason for this is that the  
ceramic capacitor will tend to shunt the inductive behavior of  
the Electrolytic capacitor at higher frequencies for an im-  
proved overall low impedance output.  
AC COUPLED VIDEO  
Many monitors and displays accept AC coupled inputs. This  
simplifies the amplification and buffering task in some re-  
spects. As can be seen in Figure 8, R1 and R2 simply set the  
input to the center of the input linear range while CIN AC  
couples the video onto the op amp’s input. The op amp is set  
for a closed loop gain of 2 with RF and RG. CG is there to  
make sure the device output is also biased at mid-supply.  
CG2 is intended to boost the high frequency gain in order to  
improve the video frequency response. This value is to be  
set and trimmed on the board to meet the application’s  
specific system requirements.  
20136449  
FIGURE 8. AC Coupled Video Amplifier/Driver  
SAG COMPENSATION  
coupling scheme due to the low frequency limit of this circuit.  
The −3 dB low frequency limit of the output circuit is given  
by:  
The capacitors shown in Figure 8 (except CG2), and espe-  
cially CO, are the large electrolytic type which are consider-  
ably costly and take up valuable real estate on the board. It  
is possible to reduce the value of the output coupling capaci-  
tor, CO, which is the largest of all, by using what is called  
SAG compensation. SAG refers to what the output video  
experiences due to the low frequency video content it con-  
tains which cannot adequately go through the output AC  
f_low_frequency (−3 dB)= 1/ (2*pi* 75*2() * CO)  
= 4.82 Hz For CO = 220 µF  
(3)  
A possible implementation of the SAG compensation is  
shown in Figure 9.  
www.national.com  
20  
Application Information (Continued)  
20136450  
FIGURE 9. AC Coupled Video Amplifier/Driver with SAG Compensation  
In this circuit, the output coupling capacitor value and size is  
greatly reduced at the expense of slightly higher op amp  
output voltage drive. Note that C1 is not only part of the SAG  
compensation, but it also sets the amplifier’s DC gain to 0 dB  
so that the output is set to mid-rail for linearity purposes. Also  
note that exceptionally high values are chosen for the R1 and  
R2 biasing resistors (510 k). The LMH6601 has extremely  
low input bias current which allows this selection thereby  
reducing the CIN value in this circuit such that CIN can even  
be a non-polar capacitors which will reduce cost.  
At high enough frequencies where both CO and C1 can be  
considered to be shorted out, R3 shunts R4 and the closed  
loop gain is determined by:  
Closed_loop_Gain (V/V)= VL/VIN = (1+ (R3||R4)/ R5)  
[RL/(RL+RO)]= 1V/V  
(4)  
At intermediate frequencies, where the CO, RO, RL path  
experiences low frequency gain loss, the R3, R5, C1 path  
provides feedback from the load side of CO. With the load  
side gain reduced at these lower frequencies, the feedback  
to the op amp inverting node reduces, causing an increase  
at the op amp’s output as a response.  
For NTSC video, low values of CO influence how much video  
black level shift occurs during the vertical blanking interval  
(1.5 ms) which has no video activity and thus is sensitive to  
CO’s charge dissipation through the load which could cause  
output SAG. An especially tough pattern is the NTSC pattern  
called “Pulse & Bar.” With this pattern the entire top and  
bottom portion of the field is black level video where for  
about 8.5 ms CO is discharging through the load with no  
video activity to replenish that charge.  
20136451  
FIGURE 10. Figure 9 Scope Photo Showing Video SAG  
There is a subtlety with the additional output drive in the SAG  
correction circuit, compared to a circuit with no SAG com-  
pensation, especially when using lower power supply volt-  
ages. This will be explained later after a brief introduction,  
below, on the effects of AC coupling on output swing.  
Figure 10 shows the output of the Figure 9 circuit with the  
scope’s cursors pointing to the SAG.  
With the circuit of Figure 9 and any other AC coupled pulse  
amplifier, the waveform duty cycle variations exert additional  
restrictions on voltage swing at any node. This is illustrated  
in the waveforms shown in Figure 11.  
21  
www.national.com  
Application Information (Continued)  
20136452  
FIGURE 11. Headroom Considerations with AC Coupled Amplifiers  
If a stage has a 3 VPP unclipped swing available at a given  
node, as shown in Figure 11, the maximum allowable ampli-  
tude for an arbitrary waveform is 1⁄  
of 3V or 1.5 VPP. This is  
2
due to the shift in the average value of the waveform as the  
duty cycle varies. Figure 11 shows what would happen if a  
2 VPP signal were applied. A low duty cycle waveform, such  
as the one in Figure 11B, would have high positive excur-  
sions. At low enough duty cycles, the waveform could get  
clipped on the top, as shown, or a more subtle loss of  
linearity could occur prior to full-blown clipping. The con-  
verse of this occurs with high duty cycle waveforms and  
negative clipping, as depicted in Figure 11C.  
Now, let’s get back to discussing the SAG compensation  
output swing subtlety hinted at earlier. For the Figure 9  
circuit, with a 1 VPP Composite Video input, the op amp  
output will swing 2 VPP because the stage gain is set to 2  
V/V. With the output set to VCC/2 (2.5V in this case), the op  
amp output voltage will range from 0.5V to 4.5V, assuming  
video duty cycle variation of 100% to 0% respectively. In  
reality, the duty cycle only approaches these extreme end  
points and it never quite gets there. Figure 12 shows the  
measured response of this circuit to show the worst case  
swing at the op amp output pin. Note that the extra output  
drive at the op amp output for SAG compensation, which  
shows up as a tilt in the upper video waveform, could cause  
clipping as the output swings even closer to the rails.  
20136453  
FIGURE 12. SAG Compensation Requires Higher  
Swing at op amp Output  
www.national.com  
22  
sheet tables) as video signals could be as large as 2 VPP  
when applied to the commonly used gain of +2 configuration.  
Because of this relatively large swing, the op amp Slew Rate  
(SR) limitation should also be considered. Table 2 shows  
these requirements for various video line rates calculated  
using a rudimentary technique and intended as a first order  
estimate only.  
Application Information (Continued)  
HOW TO PICK THE RIGHT VIDEO AMPLIFIER  
Apart from output current drive and voltage swing, the op  
amp used for a video amplifier/cable driver should also  
possess the minimum requirement for speed and slew rate.  
For video type loads, it is best to consider Large Signal  
Bandwidth (or LSBW in the National Semiconductor data  
TABLE 2. Rise Time, −3 dB BW, and Slew Rate Requirements for Various Video Line Rates  
Video  
Standard  
TV_NTSC  
VGA  
Line Rate  
(HxV)  
Refresh Rate  
Horizontal  
Active (KH%) Active (KV%)  
Vertical  
Pixel Time Rise Time LSBW  
SR  
(V/µs)  
41  
(Hz)  
30  
75  
75  
75  
75  
75  
(ns)  
118.3  
33.0  
20.3  
12.4  
7.3  
(ns)  
39.4  
11.0  
6.8  
(MHz)  
9
451x483  
640x480  
800x600  
1024x768  
1280x1024  
1600x1200  
84  
80  
76  
77  
75  
74  
92  
95  
96  
95  
96  
96  
32  
146  
237  
387  
655  
973  
SVGA  
52  
XGA  
4.1  
85  
SXGA  
2.4  
143  
213  
UXGA  
4.9  
1.6  
For any video line rate (HxV corresponding to the number of  
Active horizontal and vertical lines), the speed requirements  
can be estimated if the Horizontal Active (KH%) and Vertical  
Active (KV%) numbers are known. These percentages cor-  
respond to the percentages of the active number of lines  
(horizontal or vertical) to the total number of lines as set by  
VESA standards. Here are the general expressions and the  
specific calculations for the SVGA line rate shown in Table 2.  
The LMH6601 specifications show that it would be a suitable  
choice for video amplifiers up to and including the SVGA line  
rate as demonstrated above.  
For more information about this topic and others relating to  
video amplifiers, please see Application Note 1013:  
http://www.national.com/an/AN/AN-1013.pdf#page=1  
CURRENT TO VOLTAGE CONVERSION  
(TRANSIMPEDANCE AMPLIFIER (TIA))  
Being capable of high speed and having ultra low input bias  
current makes the LMH6601 a natural choice for Current to  
Voltage applications such as photodiode I-V conversion. In  
these type of applications, as shown in Figure 13 below, the  
photodiode is tied to the inverting input of the amplifier with  
RF set to the proper gain (gain is measured in Ohms).  
(5)  
Requiring that an “On” pixel is illuminated to at least 90% of  
its final value before changing state will result in the rise/fall  
1
time equal to, at most,  
3 the pixel time as shown below:  
(6)  
Assuming a single pole frequency response roll-off charac-  
teristic for the closed loop amplifier used, we have:  
(7)  
20136458  
Rise/Fall times are 10%-90% transition times, which for a 2  
VPP video step would correspond to a total voltage shift of  
1.6V (80% of 2V). So, the Slew Rate requirement can be  
calculated as follows:  
FIGURE 13. Typical Connection of a Photodiode  
Detector to an op amp  
(8)  
23  
www.national.com  
Application Information (Continued)  
With the LMH6601 input bias current in the femto-amperes  
range, even large values of gain (RF) do not increase the  
output error term appreciably. This allows circuit operation to  
a lower light intensity level which is always of special impor-  
tance in these applications. Most photo-diodes have a rela-  
tively large capacitance (CD) which would be even larger for  
a photo-diode designed for higher sensitivity to light because  
of its larger area. Some applications may run the photodiode  
with a reverse bias in order to reduce its capacitance with the  
disadvantage of increased contributions from both dark cur-  
rent and noise current. Figure 14 shows a typical photodiode  
capacitance plot vs. reverse bias for reference.  
20136460  
FIGURE 15. Transimpedance Amplifier Graphical  
Stability Analysis and Compensation  
Figure 15 shows that placing a capacitor, CF, with the proper  
value, across RF will create a pole in the NG function at fP.  
For optimum performance, this capacitor is usually picked so  
that NG is equal to the op amp’s open loop gain at fP. This  
will cause a “flattening” of the NG slope beyond the point of  
intercept of the two plots (open loop gain and NG) and will  
results in a Phase Margin (PM) of 45˚ assuming fP and fZ are  
at least a decade apart. This is because at the point of  
intercept, the NG pole at fP will have a 45˚ phase lead  
contribution which leaves 45˚ of PM. For reference, Figure  
15 also shows the transimpedance gain (I-V ())  
20136459  
FIGURE 14. Typical Capacitance vs. Reverse Bias  
(Source: OSI Optoelectronics)  
The diode capacitance (CD) along with the input capacitance  
of the LMH6601 (CA) has a bearing on the stability of this  
circuit and how it is compensated. With large transimped-  
ance gain values (RF), the total combined capacitance on  
the amplifier inverting input (CIN = CD + CA) will work against  
RF to create a zero in the Noise Gain (NG) function (see  
Figure 15). If left untreated, at higher frequencies where NG  
equals the open loop transfer function there will be excess  
phase shift around the loop (approaching 180˚) and there-  
fore, the circuit could be unstable. This is illustrated in Figure  
15.  
Here is the theoretical expression for the optimum CF value  
and the expected −3 dB bandwidth:  
(9)  
(10)  
Table 3, below, lists the results, along with the assumptions  
and conditions, of testing the LMH6601 with various photo-  
diodes having different capacitances (CD) at a transimped-  
ance gain (RF) of 10 k.  
www.national.com  
24  
Application Information (Continued)  
TABLE 3. Transimpedance Amplifier Figure 13 Compensation and Performance Results  
CD  
(pF)  
10  
CIN  
(pF)  
12  
CF_Calculated  
CF used  
(pF)  
1
−3 dB BW  
−3 dB BW  
Step Response  
(pF)  
1.1  
2.3  
7.2  
Calculated (MHz) Measured (MHz) Overshoot (%)  
14  
7
15  
7.0  
2.5  
6
4
9
50  
52  
3
500  
502  
8
2
CA = 2 pF  
CAPACITIVE LOAD  
GBWP = 155 MHz  
VS = 5V  
The LMH6601 can drive a capacitive load of up to 1000 pF  
with correct isolation and compensation. Figure 17 illustrates  
the in-loop compensation technique to drive a large capaci-  
tive load.  
TRANSIMPEDANCE AMPLIFIER NOISE  
CONSIDERATIONS  
When analyzing the noise at the output of the I-V converter,  
it is important to note that the various noise sources (i.e. op  
amp noise voltage, feedback resistor thermal noise, input  
noise current, photodiode noise current) do not all operate  
over the same frequency band. Therefore, when the noise at  
the output is calculated, this should be taken into account.  
The op amp noise voltage will be gained up in the region  
between the noise gain’s “zero” and its “pole” (fz and fp in  
Figure 15). The higher the values of RF and CIN, the sooner  
the noise gain peaking starts and therefore its contribution to  
the total output noise would be larger. It is obvious to note  
that it is advantageous to minimize CIN (e.g. by proper  
choice of op amp, by applying a reverse bias across the  
diode at the expense of excess dark current and noise).  
However, most low noise op amps have a higher input  
capacitance compared to ordinary op amps. This is due to  
the low noise op amp’s larger input stage.  
20136468  
FIGURE 17. In-Loop Compensation Circuit for Driving  
a Heavy Capacitive Load  
When driving a high capacitive load, an isolation resistor  
(RS) should be connected in series between the op amp  
output and the capacitive load to provide isolation and to  
avoid oscillations. A small value capacitor (CF) is inserted  
between the op amp output and the inverting input as shown  
such that this capacitor becomes the dominant feedback  
path at higher frequency. Together these components allow  
heavy capacitive loading while keeping the loop stable.  
OTHER APPLICATIONS  
There are few factors which affect the driving capability of  
the op amp:  
Op amp internal architecture  
Closed loop gain and output capacitor loading  
Table 4 shows the measured step response for various  
values of load capacitors (CL), series resistor (RS) and feed-  
back resistor (CF) with gain of +2 (RF = RG = 604) and RL  
= 2 k:  
TABLE 4. LMH6601 Step Response Summary for the  
Circuit of Figure 17  
CL  
(pF)  
10  
RS  
()  
0
CF  
(pF)  
1
t
rise/ tfall  
(ns)  
6*  
Overshoot  
(%)  
8
20136463  
50  
0
1
7*  
6
110  
300  
500  
910  
47  
6
1
10  
16  
20  
10  
10  
FIGURE 16. Charge Preamplifier Taking Advantage of  
LMH6601’s Femto-Ampere Range Input Bias Current  
10  
10  
10  
12  
80  
192  
33  
65  
* Response limited by input step generator rise time of 5 ns  
25  
www.national.com  
Application Information (Continued)  
EVALUATION BOARD  
Figure 18 shows the increase in rise/fall time (bandwidth  
decrease) at VOUT with larger capacitive loads, illustrating  
the trade-off between the two:  
National Semiconductor provides the following evaluation  
board as a guide for high frequency layout and as an aid in  
device testing and characterization. Many of the datasheet  
plots were measured with this board:  
Device  
Package  
Board Part #  
LMH6601MG  
SC70-6  
LMH730165  
This evaluation board can be shipped when a device sample  
request is placed with National Semiconductor.  
20136469  
FIGURE 18. LMH6601 In-Loop Compensation  
Response  
www.national.com  
26  
Physical Dimensions inches (millimeters) unless otherwise noted  
6-Pin SC70  
NS Package Number MA006A  
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves  
the right at any time without notice to change said circuitry and specifications.  
For the most current product information visit us at www.national.com.  
LIFE SUPPORT POLICY  
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS  
WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR  
CORPORATION. As used herein:  
1. Life support devices or systems are devices or systems  
which, (a) are intended for surgical implant into the body, or  
(b) support or sustain life, and whose failure to perform when  
properly used in accordance with instructions for use  
provided in the labeling, can be reasonably expected to result  
in a significant injury to the user.  
2. A critical component is any component of a life support  
device or system whose failure to perform can be reasonably  
expected to cause the failure of the life support device or  
system, or to affect its safety or effectiveness.  
BANNED SUBSTANCE COMPLIANCE  
National Semiconductor follows the provisions of the Product Stewardship Guide for Customers (CSP-9-111C2) and Banned Substances  
and Materials of Interest Specification (CSP-9-111S2) for regulatory environmental compliance. Details may be found at:  
www.national.com/quality/green.  
Lead free products are RoHS compliant.  
National Semiconductor  
Americas Customer  
Support Center  
National Semiconductor  
Europe Customer Support Center  
Fax: +49 (0) 180-530 85 86  
National Semiconductor  
Asia Pacific Customer  
Support Center  
National Semiconductor  
Japan Customer Support Center  
Fax: 81-3-5639-7507  
Email: new.feedback@nsc.com  
Tel: 1-800-272-9959  
Email: europe.support@nsc.com  
Deutsch Tel: +49 (0) 69 9508 6208  
English Tel: +44 (0) 870 24 0 2171  
Français Tel: +33 (0) 1 41 91 8790  
Email: ap.support@nsc.com  
Email: jpn.feedback@nsc.com  
Tel: 81-3-5639-7560  
www.national.com  

相关型号:

LMH6601MG/NOPB

具有关断状态的 250MHz、2.4V CMOS 运算放大器 | DCK | 6 | -40 to 85
TI

LMH6601MGX

250 MHz, 2.4V CMOS Op Amp with Shutdown
NSC

LMH6601MGX/NOPB

具有关断状态的 250MHz、2.4V CMOS 运算放大器 | DCK | 6 | -40 to 85
TI

LMH6601Q

250 MHz, 2.4V CMOS Operational Amplifier with Shutdown
NSC

LMH6601QMG

250 MHz, 2.4V CMOS Operational Amplifier with Shutdown
NSC

LMH6601QMG/NOPB

具有关断模式的汽车 250MHz 2.4V CMOS 运算放大器 | DCK | 6 | -40 to 85
TI

LMH6601QMGX

250 MHz, 2.4V CMOS Operational Amplifier with Shutdown
NSC

LMH6601QMGX/NOPB

250 MHz, 2.4V CMOS Operational Amplifier with Shutdown 6-SC70 -40 to 85
TI

LMH6601_09

250 MHz, 2.4V CMOS Operational Amplifier with Shutdown
NSC

LMH6609

900MHz Voltage Feedback Op Amp
NSC

LMH6609

900MHz 电压反馈运算放大器
TI

LMH6609 MDC

900MHz 电压反馈运算放大器 | Y | 0 | -40 to 85
TI