LTC6244IMS8#TRPBF [Linear]
LTC6244 - Dual 50MHz, Low Noise, Rail-to-Rail, CMOS Op Amp; Package: MSOP; Pins: 8; Temperature Range: -40°C to 85°C;
| 型号： | LTC6244IMS8#TRPBF |
| 厂家： | 
Linear |
| 描述： | LTC6244 - Dual 50MHz, Low Noise, Rail-to-Rail, CMOS Op Amp; Package: MSOP; Pins: 8; Temperature Range: -40°C to 85°C 运算放大器 放大器电路 |
| 文件： | 总24页 (文件大小：451K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC6244
Dual 50MHz, Low Noise,
Rail-to-Rail, CMOS Op Amp
U
DESCRIPTIO
FEATURES
TheLTC®6244isadualhighspeed,unity-gainstableCMOS
opampthatfeaturesa50MHzgainbandwidth,40V/µsslew
rate, 1pA of input bias current, low input capacitance and
rail-to-rail output swing. The 0.1Hz to 10Hz noise is just
■
Input Bias Current: 1pA (Typ at 25°C)
■
Low Offset Voltage: 100µV Max
■
Low Offset Drift: 2.5µV/°C Max
0.1Hz to 10Hz Noise: 1.5µV
Slew Rate: 40V/µs
■
P-P
■
■
■
■
1.5µV and 1kHz noise is guaranteed to be less than
P-P
Gain Bandwidth Product: 50MHz
Output Swings Rail-to-Rail
Supply Operation:
12nV/√Hz. This excellent AC and noise performance is
combined with wide supply range operation, a maximum
offset voltage of just 100µV and drift of only 2.5µV/°C,
making it suitable for use in many fast signal processing
applications, such as photodiode amplifiers.
2.8V to 6V LTC6244
2.8V to 5.25V LTC6244HV
Low Input Capacitance: 2.1pF
Available in 8-Pin MSOP and Tiny DFN Packages
U
■
■
This op amp has an output stage that swings within 35mV
of either supply rail to maximize the signal dynamic range
in low supply applications. The input common mode
range extends to the negative supply. It is fully specified
on 3V and 5V, and an HV version guarantees operation
on supplies of 5V.
APPLICATIO S
■
Photodiode Amplifiers
■
Charge Coupled Amplifiers
■
Low Noise Signal Processing
The LTC6244 is available in the 8-pin MSOP, and for com-
pact designs, it is packaged in the tiny dual fine pitch lead
free (DFN) package.
■
Active Filters
Medical Instrumentation
■
■
High Impedance Transducer Amplifier
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
U
TYPICAL APPLICATIO
Very Low Noise Large Area Photodiode
V
Distribution
OS
0.25pF
120
110
100
90
80
70
60
50
40
30
20
10
0
LTC6244MS8
5V PHILIPS
BF862
V
V
= 5V, 0V
S
CM
= 2.5V
1M
JFET
T
A
= 25°C
5V
V
= 1M • I
PD
OUT
4.99k
BW = 350kHz
NOISE = 291nV AT 10kHz
–5V
–
1/2
V
OUT
I
LTC6244HV
PD
4.7µF*
+
4.99k
6244 TA01a
–5V
V
BB
HAMAMATSU LARGE AREA
PHOTODIODE
–60 –40 –20
0
20
40
60
S1227-1010BQ
INPUT OFFSET VOLTAGE (µV)
C
PD
= 3000pF
6244 G01
* CAN BE MICROPHONIC, FILM, X7R, IF NEEDED.
6244f
1
LTC6244
W W U W
(Note 1)
ABSOLUTE AXI U RATI GS
Total Supply Voltage (V to V )
+
–
Specified Temperature Range (Note 3)
LTC6244 .................................................................7V
LTC6244HV...........................................................12V
Input Voltage.......................... (V + 0.3V) to (V – 0.3V)
Input Current........................................................ 10mA
Output Short Circuit Duration (Note 2) ............ Indefinite
Operating Temperature Range
LTC6244C ................................................ 0°C to 70°C
LTC6244I ............................................. –40°C to 85°C
LTC6244H.......................................... –40°C to 125°C
Junction Temperature ........................................... 150°C
DD Package ...................................................... 125°C
Storage Temperature Range................... –65°C to 150°C
DD Package ....................................... –65°C to 125°C
Lead Temperature (Soldering, 10 sec) .................. 300°C
+
–
LTC6244C ............................................ –40°C to 85°C
LTC6244I ............................................. –40°C to 85°C
LTC6244H.......................................... –40°C to 125°C
U
W
U
PACKAGE/ORDER I FOR ATIO
TOP VIEW
+
9
OUT A
–IN A
+IN A
1
2
3
4
8
7
6
5
V
TOP VIEW
+
OUT B
–IN B
+IN B
OUT A
–IN A
+IN A
1
2
3
4
8 V
A
7 OUT B
6 –IN B
5 +IN B
B
–
V
–
V
MS8 PACKAGE
8-LEAD PLASTIC MSOP
= 150°C, θ = 250°C/W
DD PACKAGE
8-LEAD (3mm 3mm) PLASTIC DFN
= 125°C, θ = 43°C/W
EXPOSED PAD (PIN 9) CONNECTED TO V
(PCB CONNECTION OPTIONAL)
T
JMAX
JA
T
JMAX
JA
–
ORDER PART NUMBER
DD PART MARKING*
ORDER PART NUMBER
MS8 PART MARKING*
LTC6244CDD
LTC6244HVCDD
LTC6244IDD
LCCF
LCGD
LCCF
LCGD
LTC6244CMS8
LTC6244HVCMS8
LTC6244IMS8
LTC6244HVIMS8
LTC6244HMS8
LTCCM
LTCGF
LTCCM
LTCGF
LTCCM
LTC6244HVIDD
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identifed by a label on the shipping container.
6244f
2
LTC6244
U
AVAILABLE OPTIO S
PART NUMBER
LTC6244CMS8
LTC6244CDD
SPECIFIED TEMP RANGE
0°C to 70°C
SPECIFIED SUPPLY VOLTAGE
3V, 5V
PACKAGE
MS8
DD
PART MARKING
LTCCM
LCCF
0°C to 70°C
3V, 5V
LTC6244HVCMS8
LTC6244HVCDD
LTC6244IMS8
LTC6244IDD
0°C to 70°C
3V, 5V, 5V
3V, 5V, 5V
3V, 5V
MS8
DD
LTCGF
LCGD
LTCCM
LCCF
0°C to 70°C
–40°C to 85°C
–40°C to 85°C
–40°C to 85°C
–40°C to 85°C
–40°C to 125°C
MS8
DD
3V, 5V
LTC6244HVIMS8
LTC6244HVIDD
LTC6244HMS8
3V, 5V, 5V
3V, 5V, 5V
3V, 5V
MS8
DD
LTCGF
LCGD
LTCCM
MS8
ELECTRICAL CHARACTERISTICS (LTC6244C/I, LTC6244HVC/I) The
●
denotes the specifications which apply
CM
over the specified temperature range, otherwise specifications are at T = 25°C. V = 5V, 0V, V = 2.5V unless otherwise noted.
A
S
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
Input Offset Voltage (Note 4)
MS8 Package
0°C to 70°C
–40°C to 85°C
40
100
225
300
µV
µV
µV
OS
●
●
DD Package
0°C to 70°C
–40°C to 85°C
100
40
650
800
950
µV
µV
µV
●
●
V
Match Channel-to-Channel (Note 5) MS8 Package
160
275
325
µV
µV
µV
OS
●
●
0°C to 70°C
–40°C to 85°C
DD Package
0°C to 70°C
–40°C to 85°C
150
800
900
1.1
µV
µV
mV
●
●
●
●
●
TC V
Input Offset Voltage Drift, MS8 (Note 6)
Input Bias Current (Notes 4, 7)
0.7
1
2.5
75
75
µV/°C
OS
I
B
pA
pA
I
OS
Input Offset Current (Notes 4, 7)
0.5
pA
pA
Input Noise Voltage
0.1Hz to 10Hz
f = 1kHz
1.5
8
µV
P-P
e
n
Input Noise Voltage Density
Input Noise Current Density (Note 8)
Input Resistance
12
nV/√Hz
fA/√Hz
Ω
i
n
0.56
12
R
Common Mode
f = 100kHz
10
IN
IN
C
Input Capacitance
Differential Mode
Common Mode
3.5
2.1
pF
pF
●
●
V
Input Voltage Range
Guaranteed by CMRR
0V ≤ V ≤ 3.5V
0
3.5
V
CM
CMRR
Common Mode Rejection
74
105
100
dB
CM
CMRR Match
Channel-to-Channel (Note 5)
●
72
dB
6244f
3
LTC6244
ELECTRICAL CHARACTERISTICS (LTC6244C/I, LTC6244HVC/I) The
●
denotes the specifications which apply
CM
over the specified temperature range, otherwise specifications are at T = 25°C. V = 5V, 0V, V = 2.5V unless otherwise noted.
A
S
SYMBOL
PARAMETER
CONDITIONS
V = 1V to 4V
MIN
TYP
MAX
UNITS
A
VOL
Large Signal Voltage Gain
O
R = 10k to V /2
1000
600
450
2500
V/mV
V/mV
V/mV
L
S
●
●
0°C to 70°C
–40°C to 85°C
V = 1.5V to 3.5V
O
R = 1k to V /2
300
200
150
1000
V/mV
V/mV
V/mV
L
S
●
●
0°C to 70°C
–40°C to 85°C
●
●
●
V
V
Output Voltage Swing Low (Note 9)
Output Voltage Swing High (Note 9)
Power Supply Rejection
No Load
SINK
SINK
15
40
35
75
mV
mV
mV
OL
I
I
= 1mA
= 5mA
150
300
●
●
●
No Load
SOURCE
SOURCE
15
45
175
35
75
325
mV
mV
mV
OH
I
I
= 1mA
= 5mA
●
PSRR
V = 2.8V to 6V, V = 0.2V
S
75
105
100
dB
CM
PSRR Match
Channel-to-Channel (Note 5)
●
●
●
●
●
●
●
73
2.8
25
dB
V
Minimum Supply Voltage (Note 10)
Short-Circuit Current
I
I
35
6.25
50
mA
mA
MHz
V/µs
MHz
ns
SC
Supply Current per Amplifier
Gain Bandwidth Product
Slew Rate (Note 11)
7.4
S
GBW
SR
Frequency = 20kHz, R = 1kΩ
35
18
L
A = –2, R = 1kΩ
V
35
L
FPBW
Full Power Bandwidth (Note 12)
Settling Time
V
OUT
= 3V , R = 1kΩ
1.9
3.7
535
P-P
L
t
s
V = 2V, A = –1, R = 1kΩ, 0.1%
STEP V L
(LTC6244C/I, LTC6244HVC/I) The
●
denotes the specifications which apply over the specified temperature range, otherwise
specifications are at T = 25°C. V = 3V, 0V, V = 1.5V unless otherwise noted.
A
S
CM
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
Input Offset Voltage (Note 4)
MS8 Package
0°C to 70°C
–40°C to 85°C
40
175
250
325
µV
µV
µV
OS
●
●
DD Package
0°C to 70°C
–40°C to 85°C
100
40
650
800
950
µV
µV
µV
●
●
V
Match Channel-to-Channel (Note 5) MS8 Package
200
300
350
µV
µV
µV
OS
●
●
0°C to 70°C
–40°C to 85°C
DD Package
0°C to 70°C
–40°C to 85°C
150
800
900
1.1
µV
µV
mV
●
●
I
I
Input Bias Current (Notes 4, 7)
Input Offset Current (Notes 4, 7)
1
pA
pA
B
●
●
75
75
0.5
pA
pA
OS
Input Noise Voltage
0.1Hz to 10Hz
f = 1kHz
1.5
8
µV
P-P
e
n
Input Noise Voltage Density
Input Noise Current Density (Note 8)
Input Voltage Range
12
nV/√Hz
fA/√Hz
V
i
n
0.56
●
V
Guaranteed by CMRR
0
1.5
CM
6244f
4
LTC6244
ELECTRICAL CHARACTERISTICS (LTC6244C/I, LTC6244HVC/I) The
●
denotes the specifications which apply
CM
over the specified temperature range, otherwise specifications are at T = 25°C. V = 3V, 0V, V = 1.5V unless otherwise noted.
A
S
SYMBOL
PARAMETER
CONDITIONS
0V ≤ V ≤ 1.5V
MIN
TYP
MAX
UNITS
●
●
CMRR
Common Mode Rejection
70
105
dB
CM
CMRR Match
Channel-to-Channel (Note 5)
68
100
800
dB
A
VOL
Large Signal Voltage Gain
V = 1V to 2V
O
R = 10k to V /2
200
100
85
V/mV
V/mV
V/mV
L
S
●
●
0°C to 70°C
–40°C to 85°C
●
●
V
V
Output Voltage Swing Low (Note 9)
Output Voltage Swing High (Note 9)
Power Supply Rejection
No Load
SINK
12
45
30
mV
mV
OL
I
= 1mA
110
●
●
No Load
= 1mA
12
50
30
110
mV
mV
OH
I
SOURCE
●
PSRR
V = 2.8V to 6V, V = 0.2V
S
75
105
dB
CM
PSRR Match
●
●
●
●
●
Channel-to-Channel (Note 5)
73
2.8
8
100
dB
V
Minimum Supply Voltage (Note 10)
Short-Circuit Current
I
I
15
4.8
50
mA
mA
MHz
SC
Supply Current per Amplifier
Gain Bandwidth Product
5.8
S
GBW
Frequency = 20kHz, R = 1kΩ
35
L
(LTC6244HVC/I) The
●
denotes the specifications which apply over the specified temperature range, otherwise specifications are at
T = 25°C. V = 5V, 0V, V = 0V unless otherwise noted.
A
S
CM
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
Input Offset Voltage (Note 4)
MS8 Package
0°C to 70°C
–40°C to 85°C
50
220
275
375
µV
µV
µV
OS
●
●
DD Package
0°C to 70°C
–40°C to 85°C
100
50
700
800
µV
µV
µV
●
●
1050
V
Match Channel-to-Channel (Note 5) MS8 Package
250
325
400
µV
µV
µV
OS
●
●
0°C to 70°C
–40°C to 85°C
DD Package
0°C to 70°C
–40°C to 85°C
150
900
1000
1100
µV
µV
µV
●
●
●
●
●
TC V
Input Offset Voltage Drift, MS8 (Note 6)
Input Bias Current (Notes 4, 7)
0.7
1
2.5
75
75
µV/°C
OS
I
B
pA
pA
I
OS
Input Offset Current (Notes 4, 7)
0.5
pA
pA
Input Noise Voltage
0.1Hz to 10Hz
f = 1kHz
1.5
8
µV
P-P
e
n
Input Noise Voltage Density
Input Noise Current Density (Note 8)
Input Resistance
12
nV/√Hz
fA/√Hz
Ω
i
n
0.56
12
R
Common Mode
f = 100kHz
10
IN
IN
C
Input Capacitance
Differential Mode
Common Mode
3.5
2.1
pF
pF
6244f
5
LTC6244
ELECTRICAL CHARACTERISTICS (LTC6244HVC/I) The
●
denotes the specifications which apply over the
specified temperature range, otherwise specifications are at T = 25°C. V = 5V, 0V, V = 0V unless otherwise noted.
A
S
CM
SYMBOL
PARAMETER
CONDITIONS
MIN
–5
TYP
MAX
UNITS
V
●
●
V
Input Voltage Range
Common Mode Rejection
Guaranteed by CMRR
–5V ≤ V ≤ 3.5V
3.5
CM
CMRR
80
105
95
dB
CM
CMRR Match
Channel-to-Channel (Note 5)
78
dB
●
A
VOL
Large Signal Voltage Gain
V = –3.5V to 3.5V
O
R = 10k
2500
1500
1200
6000
V/mV
V/mV
V/mV
L
●
●
0°C to 70°C
–40°C to 85°C
R = 1k
700
400
300
3500
V/mV
V/mV
V/mV
L
●
●
0°C to 70°C
–40°C to 85°C
●
●
●
V
V
Output Voltage Swing Low (Note 9)
Output Voltage Swing High (Note 9)
Power Supply Rejection
No Load
15
45
40
75
mV
mV
mV
OL
I
I
= 1mA
SINK
SINK
= 10mA
360
550
●
●
●
No Load
15
45
360
40
75
550
mV
mV
mV
OH
I
I
= 1mA
SOURCE
SOURCE
= 10mA
●
PSRR
V = 2.8V to 10.5V, V = 0.2V
S
75
110
106
dB
CM
PSRR Match
Channel-to-Channel (Note 5)
●
●
●
●
●
●
●
73
2.8
40
dB
V
Minimum Supply Voltage (Note 10)
Short-Circuit Current
I
I
55
7
mA
mA
MHz
V/µs
MHz
ns
SC
Supply Current per Amplifier
Gain Bandwidth Product
Slew Rate (Note 11)
8.8
S
GBW
SR
Frequency = 20kHz, R = 1kΩ
35
18
50
L
A = –2, R = 1kΩ
V
40
L
FPBW
Full Power Bandwidth (Note 12)
Settling Time
V
OUT
= 3V , R = 1kΩ
1.9
4.25
330
P-P
L
t
s
V = 2V, A = –1, R = 1kΩ, 0.1%
STEP V L
(LTC6244H) The
CM
●
denotes the specifications which apply from –40°C to 125°C, otherwise specifications are at T = 25°C. V = 5V, 0V,
A
S
V
= 2.5V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
Input Offset Voltage (Note 4)
MS8 Package
40
125
400
µV
µV
OS
●
V
Match Channel-to-Channel (Note 5) MS8 Package
40
160
400
µV
µV
OS
●
●
TC V
Input Offset Voltage Drift, MS8 (Note 6)
Input Bias Current (Notes 4, 7)
0.7
1
2.5
µV/°C
OS
I
pA
nA
B
●
2
I
Input Offset Current (Notes 4, 7)
0.5
pA
pA
OS
●
●
●
250
3.5
V
Input Voltage Range
Guaranteed by CMRR
0
V
CM
CMRR
Common Mode Rejection
0V ≤ V ≤ 3.5V
74
dB
CM
CMRR Match
Channel-to-Channel (Note 5)
●
72
dB
6244f
6
LTC6244
ELECTRICAL CHARACTERISTICS
(LTC6244H) The
●
denotes the specifications which apply from –40°C to
125°C, otherwise specifications are at T = 25°C. V = 5V, 0V, V = 2.5V unless otherwise noted.
A
S
CM
SYMBOL
PARAMETER
CONDITIONS
MIN
350
125
TYP
MAX
UNITS
V/mV
V/mV
A
VOL
Large Signal Voltage Gain
V = 1V to 4V
O
●
●
R = 10k to V /2
L
S
V = 1.5V to 3.5V
O
R = 1k to V /2
L
S
●
●
●
V
V
Output Voltage Swing Low (Note 9)
Output Voltage Swing High (Note 9)
Power Supply Rejection
No Load
SINK
SINK
40
85
mV
mV
mV
OL
I
I
= 1mA
= 5mA
325
●
●
●
No Load
SOURCE
SOURCE
40
85
325
mV
mV
mV
OH
I
I
= 1mA
= 5mA
●
PSRR
V = 2.8V to 6V, V = 0.2V
S
75
dB
CM
PSRR Match
●
●
●
●
●
●
●
Channel-to-Channel (Note 5)
73
2.8
20
dB
V
Minimum Supply Voltage (Note 10)
Short-Circuit Current
I
I
mA
SC
S
Supply Current per Amplifier
Gain Bandwidth Product
6.25
7.4
mA
GBW
SR
Frequency = 20kHz, R = 1kΩ
30
17
MHz
V/µs
MHz
L
Slew Rate (Note 11)
A = –2, R = 1kΩ
V L
FPBW
Full Power Bandwidth (Note 12)
V
OUT
= 3V , R = 1kΩ
1.8
P-P
L
(LTC6244H) The
CM
●
denotes the specifications which apply from –40°C to 125°C, otherwise specifications are at T = 25°C. V = 3V, 0V,
A
S
V
= 1.5V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
Input Offset Voltage (Note 4)
MS8 Package
40
175
400
µV
µV
OS
●
●
●
V
Match Channel-to-Channel (Note 5) MS8 Package
40
1
200
420
µV
µV
OS
I
I
Input Bias Current (Notes 4, 7)
Input Offset Current (Notes 4, 7)
pA
nA
B
2
0.5
pA
pA
OS
●
●
●
250
1.5
V
Input Voltage Range
Guaranteed by CMRR
0
V
CM
CMRR
Common Mode Rejection
0V ≤ V ≤ 1.5V
70
dB
CM
CMRR Match
●
●
Channel-to-Channel (Note 5)
68
75
dB
A
VOL
Large Signal Voltage Gain
V = 1V to 2V
O
R = 10k to V /2
V/mV
L
S
●
●
V
V
Output Voltage Swing Low (Note 9)
Output Voltage Swing High (Note 9)
Power Supply Rejection
No Load
SINK
30
mV
mV
OL
I
= 1mA
110
●
●
No Load
SOURCE
30
110
mV
mV
OH
I
= 1mA
●
PSRR
V = 2.8V to 6V, V = 0.2V
S
75
dB
CM
6244f
7
LTC6244
ELECTRICAL CHARACTERISTICS
(LTC6244H) The
●
denotes the specifications which apply from –40°C to
125°C, otherwise specifications are at T = 25°C. V = 3V, 0V, V = 1.5V unless otherwise noted.
A
S
CM
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
PSRR Match Channel-to-Channel
(Note 5)
●
●
●
●
●
73
2.8
5
dB
V
Minimum Supply Voltage (Note 10)
Short-Circuit Current
I
I
mA
mA
MHz
SC
Supply Current per Amplifier
Gain Bandwidth Product
4.8
5.8
S
GBW
Frequency = 20kHz, R = 1kΩ
28
L
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: A heat sink may be required to keep the junction temperature
below the absolute maximum rating when the output is shorted
indefinitely.
Note 3: The LTC6244C/LTC6244HVC are guaranteed to meet specified
performance from 0°C to 70°C. They are designed, characterized and
expected to meet specified performance from –40°C to 85°C, but are not
tested or QA sampled at these temperatures. The LTC6244I/LTC6244HVI,
are guaranteed to meet specified performance from –40°C to 85°C. The
LTC6244H is guaranteed to meet specified performance from –40°C to
125°C.
Note 4: ESD (Electrostatic Discharge) sensitive device. ESD protection
devices are used extensively internal to the LTC6244; however, high
electrostatic discharge can damage or degrade the device. Use proper ESD
handling precautions.
Note 6: This parameter is not 100% tested.
Note 7: This specification is limited by high speed automated test
capability. See Typical Characteristics curves for actual typical
performance.
1/2
Note 8: Current noise is calculated from the formula: i = (2qI )
n
B
–19
where q = 1.6 × 10 coulomb. The noise of source resistors up to
50GΩ dominates the contribution of current noise. See also Typical
Characteristics curve Noise Current vs Frequency.
Note 9: Output voltage swings are measured between the output and
power supply rails.
Note 10: Minimum supply voltage is guaranteed by the power supply
rejection ratio test.
Note 11: Slew rate is measured in a gain of –2 with R = 1k and R =
F
G
500Ω. V is 1V and V
slew rate is measured between –1V and
IN
OUT
+1V. On the LTC6244HV/LTC6245HV, V is 2V and V
slew rate is
IN
OUT
measured between –2V and +2V.
Note 12: Full-power bandwidth is calculated from the slew rate:
FPBW = SR/2πV .
P
Note 5: Matching parameters are the difference between the two amplifiers
of the LTC6244. CMRR and PSRR match are defined as follows: CMRR
and PSRR are measured in µV/V on the amplifiers. The difference is
calculated between the sides in µV/V. The result is converted to dB.
6244f
8
LTC6244
U W
TYPICAL PERFOR A CE CHARACTERISTICS
V
Temperature Coefficient
OS
V
Distribution
V
Distribution
Distribution
OS
OS
14
13
12
11
10
9
60
50
120
110
100
90
80
70
60
50
40
30
20
10
0
LTC6244DD
LTC6244MS8
V
V
2 LOTS
–55°C TO 125°C
LTC6244MS8
V
V
T
= 5V, 0V
= 2.5V
= 25°C
= 5V, 0V
= 2.5V
V
V
T
= 5V, 0V
= 2.5V
S
CM
A
S
CM
S
CM
= 25°C
A
40
30
8
7
6
5
4
3
2
1
20
10
0
0
–500
–350 –200 –50 100 250 400
–2.4 –1.6 –0.8
0
0.8
1.6
2.4
–60 –40 –20
0
20
40
60
INPUT OFFSET VOLTAGE (µV)
DISTRIBUTION (µV/°C)
INPUT OFFSET VOLTAGE (µV)
6244 G02
6422 G03
6244 G01
V
Temperature Coefficient
Supply Current vs Supply Voltage
(Per Amplifier)
Offset Voltage vs Input Common
Mode Voltage
OS
Distribution
11
10
9
8
7
6
5
500
400
300
200
100
0
V
= 5V, 0V
LTC6244DD
S
NORMALIZED TO
V
V
= 5V, 0V
= 2.5V
S
CM
2 LOTS
25°C V VALUE
OS
8
–55°C TO 125°C
7
6
4
3
5
4
–100
–200
–300
–400
3
2
1
0
2
T
T
T
= 125°C
= 25°C
T
T
T
= 125°C
= 25°C
= –55°C
A
A
A
A
A
A
1
= –55°C
0
–6 –5 –4 –3 –2 –1
0
1
2
3
4
5
6
0
2
4
8
10
12
6
–1 –0.5 0 0.5
1 1.5
2 2.5
3 3.5 4.5
4 5
DISTRIBUTION (µV/°C)
TOTAL SUPPLY VOLTAGE (V)
INPUT COMMON MODE VOLTAGE (V)
6422 G19
6244 G04
6244 G05
Input Bias Current vs Common
Mode Voltage
Input Bias Current vs
Common Mode Voltage
Input Bias Current vs Temperature
10000
1000
100
10
10000
1000
100
10
800
700
600
500
400
300
200
100
0
MS8 PACKAGE
MS8 PACKAGE
MS8 PACKAGE
V
= 5V, 0V
V
= 5V, 0V
S
V
= V /2
CM S
S
T
= 125°C
A
V
= 10V
S
T
T
= 85°C
= 25°C
A
A
T
A
= 125°C
V
= 5V
S
T
= 25°C
A
–100
–200
–300
–400
1
1
T
= 85°C
A
0.1
0.1
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
25 35 45 55 65 75 85 95 105 115 125
–0.8 –0.6 –0.4 –0.2
0
0.2 0.4 0.6 0.8 1.0
COMMON MODE VOLTAGE (V)
TEMPERATURE (°C)
COMMON MODE VOLTAGE (V)
6244 G06
6244 G08
6244 G07
6244f
9
LTC6244
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Output Saturation Voltage
vs Load Current (Output Low)
Output Saturation Voltage
vs Load Current (Output High)
Gain Bandwidth and Phase
Margin vs Temperature
10
1
10
1
80
60
40
20
0
V
= 5V, 0V
V
= 5V, 0V
S
S
V
=
5V
S
PHASE
MARGIN
V
=
1.5V
S
70
60
50
40
–20
GAIN
BANDWIDTH
0.1
0.01
0.1
0.01
V
=
5V
S
T
T
T
= 125°C
= 25°C
T
T
T
= 125°C
= 25°C
A
A
A
A
A
A
C
= 5pF
= 1k
L
L
= –55°C
= –55°C
R
V
=
S
1.5V
30
0.1
1
10
100
0.1
1
10
100
–55 –35 –15
5
25 45
TEMPERATURE (°C)
125
65 85 105
LOAD CURRENT (mA)
LOAD CURRENT (mA)
6244 G10
6244 G09
6244 G11
Gain Bandwidth and Phase
Margin vs Supply Voltage
Open Loop Gain vs Frequency
Slew Rate vs Temperature
100
90
80
70
60
50
40
30
20
10
0
120
60
50
40
30
50
48
46
44
42
40
38
36
34
32
30
28
C
R
V
= 5pF
T
= 25°C
= 5pF
= 1k
A
= –2
L
L
A
L
L
V
F
100
80
= 1k
C
R
= 1k, R = 500Ω
G
PHASE
= V /2
R
CONDITIONS: SEE NOTE 11
CM
S
PHASE MARGIN
60
40
20
GAIN
0
70
FALLING
RISING
–20
–40
–60
–80
–100
–120
60
50
40
GAIN BANDWIDTH
V
S
V
S
=
=
5V
1.5V
V
S
V
S
=
=
5V
2.5V
–10
–20
0
4
6
8
10
12
10k
100k
1M
FREQUENCY (Hz)
10M
100M
2
–50
0
25
50
75 100 125
–25
TOTAL SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
6244 G12
6244 G13
6244 G14
Common Mode Rejection Ratio
vs Frequency
Output Impedance vs Frequency
Channel Separation vs Frequency
110
100
90
80
70
60
50
40
30
20
10
0
0
–10
1000
100
10
T
= 25°C
= 2.5V
T
V
A
= 25°C
T
= 25°C
= 2.5V
A
S
A
S
V
A
S
V
=
2.5V
V
= 1
–20
–30
–40
–50
A
= 10
V
A
= 2
V
–60
1
–70
A
= 1
V
–80
0.1
–90
–100
–110
–120
0.01
0.001
–10
10k
100k
1M
10M
100M
10k
100
1M
10M
100M
10k
100k
1M
FREQUENCY (Hz)
10M
100M
FREQUENCY (Hz)
FREQUENCY (Hz)
6244 G16
6244 G17
6244 G15
6244f
10
LTC6244
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Power Supply Rejection Ratio
vs Frequency
Output Short-Circuit Current
vs Power Supply Voltage
Minimum Supply Voltage
300
250
200
150
100
50
50
40
100
90
80
70
60
50
40
30
20
10
0
V
= V /2
S
T
= 25°C
CM
A
S
V
= 2.5V
NEGATIVE
SUPPLY
30
20
SINKING
POSITIVE
SUPPLY
10
0
0
–50
–100
–150
–200
–250
–300
–10
–20
–30
–40
–50
SOURCING
T
T
T
= 125°C
= 25°C
T
T
T
= 125°C
= 25°C
= –55°C
A
A
A
A
A
A
= –55°C
–10
0
1
2
3
4
5
6
7
8
9
10
2.5
3
3.5
4
5
1.5
4.5
2
1k
10k
100k
1M
10M
100M
POWER SUPPLY VOLTAGE ( V)
TOTAL SUPPLY VOLTAGE (V)
FREQUENCY (Hz)
6244 G18
6244 G20
6244 G21
Open-Loop Gain
Open-Loop Gain
Open-Loop Gain
–40
–50
–40
–50
–40
–50
T = 25°C
A
V = 3V, 0V
S
–60
–60
–60
R
= 100k
= 10k
–70
L
–70
–80
–70
–80
–80
R
L
–90
–90
–90
–100
–100
–100
–110
–110
–110
–5
–2
0
1
2
3
4
5
2
3
–4 –3
–1
5
4.5
0
0.5
1
1.5
2.5
0
1.5
3
3.5
4
0.5
1
2
2.5
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
6244 G22
6244 G23
6244 G22
Noise Voltage vs Frequency
Offset Voltage vs Output Current
Warm-Up Drift vs Time
200
150
100
50
40
35
30
25
20
15
10
5
–5
–10
–15
–20
–25
–30
–35
–40
–45
V
=
5V
T
A
S
CM
= 25°C
2.5V
= 0V
T
= 25°C
S
A
V
V
=
V
=
1.5V
S
T
= 125°C
A
V
=
5V
S
0
T
= 25°C
A
–50
–100
–150
– 200
V
=
2.5V
T
= –55°C
S
A
0
–50 –40 –30 –20 –10
0
10 20 30 40 50
10
100
1k
10k
100k
30 35
40 45 50 55 60
0
5
10 15 20 25
FREQUENCY (Hz)
OUTPUT CURRENT (mA)
TIME AFTER POWER UP (SEC)
6244 G27
6244 G25
6244 G26
6244f
11
LTC6244
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Series Output Resistance and
Overshoot vs Capacitive Load
0.1Hz to 10Hz Voltage Noise
Noise Current vs Frequency
60
50
40
30
20
10
0
1000
100
10
V
V
A
= 100mV
2.5V
T
V
V
= 25°C
OUT
V
= 5V, 0V
A
S
S
=
=
2.5V
= 0V
S
= –2
V
CM
30pF
1k
–
R
= 10Ω
S
500Ω
R
S
+
C
L
1
R
= 50Ω
S
0.1
10
100
1000
100
1k
10k
100k
TIME (1s/DIV)
CAPACITIVE LOAD (pF)
FREQUENCY (Hz)
6244 G30
6244 G29
6244 G28
Series Output Resistance and
Overshoot vs Capacitive Load
Series Output Resistance and
Overshoot vs Capacitive Load
Settling Time vs Output Step
(Noninverting)
60
50
40
30
20
10
0
60
50
40
30
20
10
0
900
800
700
600
500
400
300
200
100
0
V
V
A
= 100mV
2.5V
V
A
T
=
5V
NOTE: EXCEEDS INPUT
COMMON MODE RANGE
V
V
A
= 100mV
2.5V
OUT
S
V
A
OUT
R
= 10Ω
=
= 1
=
S
S
S
= –1
= 25°C
= 1
V
V
30pF
R
= 10Ω
S
–
+
V
OUT
1k
–
V
IN
1k
1k
R
S
+
R
= 50Ω
S
C
L
1mV
1mV
–
+
R
S
R
= 50Ω
S
10mV
10mV
C
L
10
100
1000
0
1
–4 –3 –2 –1
2
3
4
10
100
CAPACITIVE LOAD (pF)
1000
CAPACITIVE LOAD (pF)
OUTPUT STEP (V)
6244 G31
6244 G32
6244 G33
Settling Time vs Output Step
(Inverting)
Maximum Undistorted Output
Signal vs Frequency
Distortion vs Frequency
–30
–40
–50
–60
–70
–80
–90
–100
900
800
700
600
500
400
300
200
100
0
10
9
8
7
6
5
4
3
2
1
V
A
T
= 5V
V
A
V
=
2.5V
= +1
= 2V
S
V
A
S
V
1k
1k
–
+
= –1
V
IN
V
OUT
= 25°C
OUT
P-P
1k
R
= 1k, 2ND
L
1mV
1mV
A
= +2
V
R
= 1k, 3RD
L
10mV
2
10mV
A
= –1
V
=
5V
V
S
A
T
= 25°C
HD2, HD3 < –40dBc
0
1
10k
100k
1M
10M
–4 –3 –2 –1
3
4
10k
100k
1M
10M
OUTPUT STEP (V)
FREQUENCY (Hz)
FREQUENCY (Hz)
6244 G36
6244 G35
6244 G34
6244f
12
LTC6244
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Distortion vs Frequency
Distortion vs Frequency
Distortion vs Frequency
–30
–40
–50
–60
–70
–80
–90
–100
–30
–40
–50
–60
–70
–80
–90
–100
–30
–40
–50
–60
–70
–80
–90
–100
V
A
V
=
5V
= +2
= 2V
V
A
V
=
2.5V
= +2
= 2V
V
A
V
=
5V
= +1
= 2V
S
V
S
V
S
V
OUT
P-P
OUT
P-P
OUT
P-P
R
= 1k, 2ND
R
= 1k, 2ND
R
= 1k, 2ND
L
L
L
R
= 1k, 3RD
L
R
= 1k, 3RD
R
= 1k, 3RD
L
L
10k
100k
1M
10M
10k
100k
1M
10M
10k
100k
1M
10M
FREQUENCY (Hz)
FREQUENCY (Hz)
FREQUENCY (Hz)
6244 G39
6244 G37
6244 G38
Large-Signal Response
Small-Signal Response
Small-Signal Response
0V
0V
0V
6244 G40
6244 G41
6244 G42
V
A
=
2.5V
200ns/DIV
V
A
=
2.5V
200ns/DIV
V
A
=
5V
2µs/DIV
S
V
L
S
V
L
L
S
V
L
= 1
= 1
= 1
R
= ∞
R
= ∞
= 75pF
R
= ∞
C
Output Overdrive Recovery
Large-Signal Response
V
IN
0V
0V
1V/DIV
0V
V
OUT
2V/DIV
6244 G43
6244 G44
V
A
=
= –1
= 1k
2.5V
200ns/DIV
V
A
=
2.5V
200ns/DIV
S
V
L
S
V
L
= 3
R
R
= 3k
6244f
13
LTC6244
U
W U U
APPLICATIO S I FOR ATIO
Amplifier Characteristics
ESD
TheLTC6244hasreverse-biasedESDprotectiondiodeson
all input and outputs as shown in Figure 1. These diodes
protect the amplifier for ESD strikes to 4kV. If these pins
are forced beyond either supply, unlimited current will
flow through these diodes. If the current transient is less
than 1 second and limited to one hundred milliamps or
less, no damage to the device will occur.
Figure 1 is a simplified schematic of the LTC6244, which
has a pair of low noise input transistors M1 and M2. A
simple folded cascode Q1, Q2 and R1, R2 allow the input
stage to swing to the negative rail, while performing level
shift to the Differential Drive Generator. Low offset voltage
is accomplished by laser trimming the input stage.
Capacitor C1 reduces the unity cross frequency and im-
proves the frequency stability without degrading the gain
The amplifier input bias current is the leakage current of
these ESD diodes. This leakage is a function of the tem-
perature and common mode voltage of the amplifier, as
shown in the Typical Performance Chacteristics.
bandwidth of the amplifier. Capacitor C sets the overall
M
amplifier gain bandwidth. The differential drive generator
supplies signals to transistors M3 and M4 that swing the
output from rail-to-rail.
Noise
The photo of Figure 2 shows the output response to an
input overdrive with the amplifier connected as a voltage
follower. If the negative going input signal is less than
The LTC6244 exhibits low 1/f noise in the 0.1Hz to 10Hz
region. This 1.5µV noise allows these op amps to be
P-P
–
used in a wide variety of high impedance low frequency
applications, where Zero-Drift amplifiers might be inap-
propriate due to their input sampling characteristic.
a diode drop below V , no phase inversion occurs. For
–
input signals greater than a diode drop below V , limit the
current to 3mA with a series resistor R to avoid phase
S
inversion.
In the frequency region above 1kHz the LTC6244 also
shows good noise voltage performance. In this frequency
region, noise can easily be dominated by the total source
The input common mode voltage range extends from
–
+
V to V – 1.5V. In unity gain voltage follower applications,
exceeding this range by applying a signal that reaches 1V
fromthepositivesupplyrailcancreatealowlevelinstability
at the output. Loading the amplifier with several hundred
micro-amps will reduce or eliminate the instability.
+
V
2.5V
+
V
–
+
I
TAIL
V
V
M3
CM
DESD1
+
DESD2
DESD4
–
+
V
V
V
–2.5V
DESD5
V
V
M1
M2
IN
DIFFERENTIAL
DRIVE
GENERATOR
–
IN
V
O
V
AND V OF FOLLOWER WITH LARGE INPUT OVERDRIVE
IN
OUT
DESD6
DESD3
C1
+2.5V
–
–
+
–
V
V
V
Q1
+
Q2
BIAS
M4
1/2
R
S
V
OUT
LTC6244
0Ω
–
V
R1
R2
IN
–2.5V
–
V
6244 F01
6244 F02
Figure 2. Unity Gain Follower Test Circuit
Figure 1. Simplified Schematic
6244f
14
LTC6244
U
W U U
APPLICATIO S I FOR ATIO
resistance of the particular application. Specifically, these
amplifiers exhibit the noise of a 4k resistor, meaning it is
desirable to keep the source and feedback resistance at or
In low gain configurations and with R and R in even
F S
the kilohm range (Figure 3), this pole can create excess
phase shift and possibly oscillation. A small capacitor C
F
below this value, i.e., R + R ||R ≤ 4k. Above this total
in parallel with R eliminates this problem.
S
G
FB
F
source impedance, the noise voltage is not dominated by
Achieving Low Input Bias Current
the amplifier.
The DD package is leadless and makes contact to the PCB
beneath the package. Solder flux used during the attach-
ment of the part to the PCB can create leakage current
paths and can degrade the input bias current performance
ofthepart. Allinputsaresusceptiblebecausethebackside
Noise current can be estimated from the expression i =
n
–19
√2qI , where q = 1.6 • 10 coulombs. Equating √4kTRΔf
B
and R √2qI Δf shows that for source resistors below
S
B
50GΩ the amplifier noise is dominated by the source
resistance. See the Typical Characteristics curve Noise
Current vs Frequency.
–
paddle is connected to V internally. As the input voltage
–
changes or if V changes, a leakage path can be formed
Proprietary design techniques are used to obtain simulta-
neous low 1/f noise and low input capacitance. Low input
capacitance is important when the amplifier is used with
high source and feedback resistors. High frequency noise
and alter the observed input bias current. For lowest bias
current, use the LTC6244 in the MS8 package.
Photodiode Amplifiers
from the amplifier tail current source, I
in Figure 1,
TAIL
Photodiodes can be broken into two categories: large area
photodiodes with their attendant high capacitance (30pF
to 3000pF) and smaller area photodiodes with relatively
lowcapacitance(10pForless).Foroptimalsignal-to-noise
performance, atransimpedanceamplifierconsistingofan
invertingopampandafeedbackresistorismostcommonly
usedtoconvertthephotodiodecurrentintovoltage. Inlow
noise amplifier design, large area photodiode amplifiers
require more attention to reducing op amp input voltage
noise, while small area photodiode amplifiers require
more attention to reducing op amp input current noise
and parasitic capacitances.
couplesthroughtheinputcapacitanceandappearsacross
these large source and feedback resistors.
Stability
The good noise performance of these op amps can be
attributed to large input devices in the differential pair.
Above several hundred kilohertz, the input capacitance
can cause amplifier stability problems if left unchecked.
When the feedback around the op amp is resistive (R ), a
F
pole will be created with R , the source resistance, source
F
capacitance (R , C ), and the amplifier input capacitance.
S
S
C
F
R
F
–
+
C
IN
OUTPUT
6244 F03
R
C
S
S
Figure 3. Compensating Input Capacitance
6244f
15
LTC6244
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APPLICATIO S I FOR ATIO
Large Area Photodiode Amplifiers
amp voltage noise and the noise gain. For reference, the
DC output offset of this circuit is about 100µV, bandwidth
A simple large area photodiode amplifier is shown in
Figure 4a. The capacitance of the photodiode is 3650pF
(nominally 3000pF), and this has a significant effect on
the noise performance of the circuit. For example, the
photodiodecapacitanceat10kHzequatestoanimpedance
of 4.36kΩ, so the op amp circuit with 1MΩ feedback has a
noise gain of NG = 1 + 1M/4.36k = 230 at that frequency.
Therefore, the LTC6244 input voltage noise gets to the
output as NG • 7.8nV/√Hz = 1800nV/√Hz, and this can
clearly be seen in the circuit’s output noise spectrum in
Figure 4b. Note that we have not yet accounted for the
op amp current noise, or for the 130nV/√Hz of the gain
resistor, but these are obviously trivial compared to the op
is 52kHz, and the total noise was measured at 1.7mV
on a 100kHz measurement bandwidth.
RMS
An improvement to this circuit is shown in Figure 5a,
where the large diode capacitance is bootstrapped by a
1nV/√Hz JFET. This depletion JFET has a V of about
GS
–0.5V, so that R
forces it to operate at just over 1mA of
BIAS
drain current. Connected as shown, the photodiode has a
reverse bias of one V , so its capacitance will be slightly
GS
lower than in the previous case (measured 2640pF), but
the most drastic effects are due to the bootstrapping.
Figure 5b shows the output noise of the new circuit.
Noise at 10kHz is now 220nV/√Hz, and the 130nV/√Hz
noise thermal noise floor of the 1M feedback resistor
is discernible at low frequencies. What has happened is
that the 7.8nV/√Hz of the op amp has been effectively
replaced by the 1nV/√Hz of the JFET. This is because the
1M feedback resistor is no longer “looking back” into the
large photodiode capacitance. It is instead looking back
intoaJFETgatecapacitance,anopampinputcapacitance,
and some parasitics, approximately 10pF total. The large
photodiode capacitance is across the gate-source volt-
age of the low noise JFET. Doing a sample calculation at
10kHz as before, the photodiode capacitance looks like
6kΩ, so the 1nV/√Hz of the JFET creates a current noise
of 1nV/6k = 167fA/√Hz. This current noise necessarily
flows through the 1M feedback resistor, and so appears
as 167nV/√Hz at the output. Adding the 130nV/√Hz of the
resistor (RMS wise) gives a total calculated noise density
of 210nV/√Hz, agreeing well with the measured noise of
Figure 5b. Another drastic improvement is in bandwidth,
now over 350kHz, as the bootstrap enabled a reduction
of the compensating feedback capacitance. Note that the
bootstrap does not affect the DC accuracy of the amplifier,
except by adding a few picoamps of gate current.
C
F
3.9pF
R
F
1M
5V
V
= 1M • I
PD
OUT
I
PD
BW = 52kHz
NOISE = 1800nV/√Hz AT 10kHz
–
1/2
LTC6244HV
HAMAMATSU
LARGE AREA
PHOTODIODE
S1227-1010BQ
V
OUT
+
6244 F04a
–5V
C
PD
= 3000pF
Figure 4a. Large Area Photodiode Transimpedance Amplifier
1k
10k
100k
FREQUENCY (Hz)
6244 F04b
There is one drawback to this circuit. Most photodiode
circuits require the ability to set the amount of applied
reverse bias, whether it’s 0V, 5V, or 200V. This circuit has
a fixed reverse bias of about 0.5V, dictated by the JFET.
Figure 4b. Output Noise Spectral Density of the Circuit of Figure
4a. At 10kHz, the 1800nV/√Hz Output Noise is Due Almost
Entirely to the 7.8nV Voltage Noise of the LTC6244 and the High
Noise Gain of the 1M Feedback Resistor Looking Into the High
Photodiode Capacitance
6244f
16
LTC6244
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APPLICATIO S I FOR ATIO
C
F
C
F
0.25pF
0.25pF
5V
PHILIPS
BF862
JFET
5V PHILIPS
BF862
R
F
1M
R
F
1M
JFET
5V
5V
R
4.99k
V
= 1M • I
V
= 1M • I
PD
BIAS
OUT
PD
OUT
I
PD
4.99k
BW = 350kHz
BW = 250kHz
–5V
–5V
–
–
OUTPUT NOISE = 220nV/√Hz
OUTPUT NOISE = 291nV/√Hz
1/2
LTC6244HV
1/2
LTC6244HV
AT10kHz
AT 10kHz
HAMAMATSU
LARGE AREA
PHOTODIODE
V
V
OUT
OUT
4.7µF
X7R
I
PD
+
+
S1227-1010BQ
= 3000pF
4.99k
6244 F04a
6244 F06a
–5V
–5V
C
PD
V
BB
HAMAMATSU LARGE AREA
PHOTODIODE
Figure 5a. Large Area Diode Bootstrapping
S1227-1010BQ
C
= 3000pF
PD
Figure 6a. The Addition of a Capacitor and Resistor Enable the
Benefit of Bootstrapping While Applying Arbitrary Photodiode
Bias Voltage V
BB
1k
10k
100k
FREQUENCY (Hz)
6244 F05b
Figure 5b: Output Noise Spectral Density of Figure 5a. The
Simple JFET Bootstrap Improves Noise (and Bandwidth)
Drastically. Noise Density at 10kHz is Now 220nV/√Hz, About
a 8.2x Reduction. This is Mostly Due to the Bootstrap Effect
of Swapping the 1nV/√Hz of the JFET for the 7.8nV/√Hz of the
Op Amp
1k
10k
100k
6244 F06b
FREQUENCY (Hz)
Figure 6b: Output Spectrum of Circuit of Figure 6a, with
Photodiode Bias at 0V. Photodiode Capacitance is Back Up,
as in the Original Circuit of Figure 4a. However, it can be
Reduced Arbitrarily by Providing Reverse Bias. This Plot
Shows that Bootstrapping Alone Reduced the 10kHz Noise
Density by a Factor of 6.2, from 1800nV/√Hz to 291nV/√Hz.
The solution is as shown in the circuit of Figure 6a, which
uses a capacitor-resistor pair to enable the AC benefits of
bootstrappingwhileallowingadifferentreverseDCvoltage
on the photodiode. The JFET is still running at the same
current, but an arbitrary reverse bias may be applied to
the photodiode. The output noise spectrum of the circuit
with 0V of photodiode reverse bias is shown in Figure 6b.
Photodiode capacitance is again 3650pF, as in the original
circuit of Figure 4a. This noise plot with 0V bias shows
that bootstrapping alone was responsible for a factor of
6.2 noise reduction, from 1800nV/√Hz to 291nV/√Hz at
10kHz, independent of photodiode capacitance. However,
photodiodecapacitancecannowcanbereducedarbitrarily
by providing reverse bias, and the photodiode can also be
reversed to support either cathode or anode connections
for positive or negative going outputs.
The circuit on the last page of this data sheet shows fur-
ther reduction in noise by paralleling four JFETs to attain
152nV/√Hz at 10kHz, a noise of 12 times less than the
basic photodiode circuit of Figure 4a.
6244f
17
LTC6244
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APPLICATIO S I FOR ATIO
Small Area Photodiode Amplifiers
grounded), or about 6pF total. The small photodiode has
1.8pF,sotheinputcapacitanceoftheamplifierisdominating
the capacitance. The small feedback capacitor is an actual
component (AVX Accu-F series), but it is also in parallel
with the op amp lead, resistor and parasitic capacitances,
so the total real feedback capacitance is probably about
0.4pF. The reason this is important is that this sets the
compensation of the circuit and, with op amp gain band-
width, the circuit bandwidth. The circuit as shown has a
Smallareaphotodiodeshaveverylowcapacitance,typically
under 10pF and some even below 1pF. Their low capaci-
tance makes them more approximate current sources to
higher frequencies than large area photodiodes. One of
the challenges of small area photodiode amplifier design
is to maintain low input capacitance so that voltage noise
does not become an issue and current noise dominates. A
simplesmallareaphotodiodeamplifierusingtheLTC6244
is shown in Figure 7. The input capacitance of the ampli-
bandwidth of 350kHz, with an output noise of 120µV
measured over that bandwidth.
RMS
fier consists of C and one C (because the +input is
DM
CM
The circuit of Figure 8a makes some slight improvements.
Operation is still transimpedance mode, with R setting
F
C
F
0.1pF
the gain to 1MΩ. However, a noninverting input stage A1
with a gain of 3 has been inserted, followed by the usual
inverting stage performed by A2. Note what this achieves.
The amplifier input capacitance is bootstrapped by the
feedback of R2:R1, eliminating the effect of A1’s input
R
F
1M
V
= 1M • I
PD
OUT
BW = 350kHz
NOISE = 120 V
5V
I
PD
RMS
MEASURED ON A
350kHz BW
SMALL AREA
PHOTODIODE
VISHAY
–
C
(3.5pF), and leaving only one C (2.1pF). The op
DM
CM
1/2
V
OUT
amp at Pins 5, 6 and 7 was chosen for the input amplifier
to eliminate extra pin-to-pin capacitance on the (+) input.
The lead capacitance on the corner of an MSOP package is
only about 0.15pF. By using this noninverting configura-
tion, input capacitance is minimized.
LTC6244HV
TEMD1000
+
C
= 1.8pF
PD
–5V
6244 F07
–5V
Figure 7. LTC6244 in a Normal TIA Configuration
0.07pF
(PARASITIC)
R
F
1M
R4
6.98k
5V
V
= 1M • I
OUT PD
I
PD
BW = 1.6MHz
NOISE = 1.2mV
5
6
SMALL AREA
PHOTODIODE
VISHAY
8
R3
1k
+
RMS
C2
A1 1/2
LTC6244HV
MEASURED ON A
2MHz BW
7
2
3
150pF
–
TEMD1000
A2 1/2
LTC6244HV
1
V
C
= 1.8pF
–
OUT
PD
6244 F08a
R2
1k
–5V
+
4
C1
56pF
R1
499
–5V
Figure 8a: Using Both Op Amps for Higher Bandwidth. A1 Provides a Gain of 3 Within the Loop, Increasing the Gain Bandwidth
Product. This Bootstraps the C Accross A1’s Inputs, Reducing Amplifier Input Capacitance. Inversion is Provided by A2, so that
DM
the Photodiode Looks Into a Noninverting Input. Pin 5 was Selected Because it is in the Corner, Removing One Lead Capacitance
6244f
18
LTC6244
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APPLICATIO S I FOR ATIO
adding appreciable noise to the circuit. In addition, add-
ing gain to low level signals over appreciable bandwidth
is extremely useful. A typical application for a low noise,
high impedance, differential amplifier is in the baseband
circuit of an RFID (radio frequency identification) receiver.
The baseband signal of a UHF RFID receiver is typically a
low level differential signal at the output of a demodulator
with differential output impedance in the range of 100Ω to
400Ω. The bandwidth of this signal is 1MHz or less.
Total capacitance at the amplifier’s input is now one C
CM
(2.1pF) plus the photodiode capacitance C (1.8pF), or
PD
about4pFaccountingforparasitics. Theshuntimpedance
at 1MHz, for example, is X = 1/(2πfC) = 39.8kΩ, and
C
therefore, the noise gain at 1MHz is NG = 1+Rf/X = 26.
C
Theinputvoltagenoiseofthisamplifierisabout15nV/√Hz,
after accounting for the effects of R1 through R3, the
noise of the second stage and the fact that voltage noise
does rise with frequency. Multiplying the noise gain by
the input voltage noise gives an output noise density due
to voltage noise of 26 • 15nV/√Hz = 390nV/√Hz. But the
noise spectral density plot of Figure 8b shows an output
noise of 782nV/√Hz at 1MHz. The extra output noise is
due to input current noise, multiplied by the feedback
impedance. So while the circuit of Figure 8a does increase
bandwidth, it does not offer a noise advantage. Note,
The circuit of Figure 9a uses an LTC6244 to make a low
noise fully differential amplifier. The amplifier’s gain, input
impedanceand–3dBbandwidthcanbespecifiedindepen-
dently. Knowing the desired gain, input impedance and
–3dB bandwidth, R , C and C can be calculated from
G
F
IN
the equations shown in Figure 9b. The common mode
gain of this amplifier is equal to one (V = V
)
INCM
OUTCM
however, that the 1.2mV
of noise is now measured in
RMS
and is independent of resistor matching. The component
values in the Figure 9a circuit implement a 970kHz, gain
= 5, differential amplifier with 4k input impedance. The
output differential DC offset is typically less than 500µV.
The differential input referred noise voltage density is
shown in Figure 10. The total input referred noise in a
a 2MHz bandwidth, instead of over a 350kHz bandwidth
of the previous example.
A Low Noise Fully Differential Buffer/Amplifier
In differential signal conditioning circuits, there is often a
need to monitor a differential source without loading or
1MHz bandwidth is 16µV
.
RMS
50k
1M
FREQUENCY (Hz)
5M
6244 F08b
Figure 8b: Output Noise Spectrum of the Circuit in Figure 8a.
Noise at 1MHz is 782nV/√Hz, Due Mostly to the Input Current
Noise Rising with Frequency
6244f
19
LTC6244
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APPLICATIO S I FOR ATIO
f
= 970kHz
–3dB
32
28
24
20
16
12
8
+
GAIN = 5
= 4k
1/2
+
R
IN
V
OUT
LTC6244
–
C
F
33pF
R
IN
R
G
2k
+
10k
2k
2k
2k
V
V
IN
C
IN
4
82pF
10k
100k
FREQUENCY (Hz)
1M
6244 F10
C
IN
82pF
R
IN
Figure 10. Differential Input Referred Noise
R
G
2k
10k
–
IN
C
F
33pF
2k
A Low Noise AC Difference Amplifier
+
In the signal conditioning of wideband sensors and trans-
ducers, a low noise amplifier is often used to provide gain
for low level AC difference signals in the frequency range
of a few Hertz to hundreds of kilo-Hertz. In addition, the
amplifiermustrejectcommonmodeACsignalsanditsinput
impedance should be higher than the differential source
impedance. Typical applications are piezoelectric sensors
used in sonar, sound and ultrasound systems and LVDT
(linearvariabledifferentialtransformers)fordisplacement
measurements in process control and robotics.
V
–
1/2
LTC6244
–
V
OUT
6244 F09a
+
–
V
Figure 9a. Low Noise Fully Differential Buffer/Amplifier
(f
–3dB
= 970kHz, Gain = 5, R = 4k)
IN
Input Impedance = 2 • RIN
The Figure 11a circuit is a low noise, single supply AC
difference amplifier. The amplifier’s low frequency –3dB
bandwidth is set with resistor R5 and capacitor C3, while
the upper –3dB bandwidth is set with R2 and C1. The
+
–
VOUT – VOUT
RG
RIN
Gain =
=
+
–
V
– V
IN
IN
input common mode DC voltage can vary from ground to
5MHz
f3dB
+
V and the output DC voltage is equal to the V voltage.
Maximum Gain =
REF
The amplifier’s gain is the ratio of resistors R2 to R1 (R4
= R2 and R3 = R1). The component values in the circuit
of Figure 11a implement an 800Hz to 160kHz AC ampli-
fier with a gain equal to 10 and 12nV/√Hz input referred
voltage noise density shown in Figure 11b. The total input
1
CF =
4398 • f3dB • Gain + 2
(
)
Gain + 2
CIN =
referred wideband noise is 4.5µV , in the bandwidth
RMS
of 500Hz to 200kHz.
8.977 • Gain •RIN • f3dB
1
f3dB
=
4000 • π2 •RG • CF • CIN
Figure 9b. Design Equations for Figure 9a Circuit
6244f
20
LTC6244
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APPLICATIO S I FOR ATIO
C1
47pF
R1
2k
R2
20k
V1
–
1/2 LTC6244
+
V
OUT
C3
1000pF
+
V
R5
200k
R3
2k
–
+
R4
20k
V2
1/2 LTC6244
C2
47pF
V
REF
6244 F11a
VOUT = GAIN • V2 – V1 + V
(
)
REF
R2
R1
GAIN =
R3 = R1, R4 = R2, C1= C2
BANDWIDTH = fHI – fLO
1
1
fHI
=
, fLO =
2 • π •R2 •C1
2 • π •R5 •C3
Figure 11a. Low Noise AC Difference Amplifier
(Bandwidth 800Hz to 160kHz, Gain = 10)
BW = 800Hz TO 160kHz
GAIN = 10
28
24
20
16
12
8
4
0
1
10
1000
FREQUENCY (kHz)
6244 F11b
Figure 11b. Input Referred Noise
6244f
21
LTC6244
U
PACKAGE DESCRIPTIO
DD Package
8-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1698)
0.675 0.05
3.5 0.05
2.15 0.05 (2 SIDES)
1.65 0.05
PACKAGE
OUTLINE
0.25 0.05
0.50
BSC
2.38 0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
R = 0.115
0.38 0.10
TYP
5
8
3.00 0.10
(4 SIDES)
1.65 0.10
(2 SIDES)
PIN 1
TOP MARK
(NOTE 6)
(DD8) DFN 1203
4
1
0.25 0.05
0.75 0.05
0.200 REF
0.50 BSC
2.38 0.10
(2 SIDES)
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-1)
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON TOP AND BOTTOM OF PACKAGE
6244f
22
LTC6244
U
PACKAGE DESCRIPTIO
MS8 Package
8-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1660)
0.889 0.127
(.035 .005)
5.23
(.206)
MIN
3.20 – 3.45
(.126 – .136)
3.00 0.102
(.118 .004)
(NOTE 3)
0.52
(.0205)
REF
0.65
(.0256)
BSC
0.42 0.038
(.0165 .0015)
TYP
8
7 6
5
RECOMMENDED SOLDER PAD LAYOUT
3.00 0.102
(.118 .004)
(NOTE 4)
4.90 0.152
(.193 .006)
DETAIL “A”
0.254
(.010)
0° – 6° TYP
GAUGE PLANE
1
2
3
4
0.53 0.152
(.021 .006)
1.10
(.043)
MAX
0.86
(.034)
REF
DETAIL “A”
0.18
(.007)
SEATING
PLANE
0.22 – 0.38
0.127 0.076
(.009 – .015)
(.005 .003)
0.65
(.0256)
BSC
TYP
MSOP (MS8) 0204
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
6244f
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
23
LTC6244
TYPICAL APPLICATION
Ultralow Noise Large Area Photodiode Amplifier
5V
J4
–5V
Photodiode Amplifier Output
Noise Spectal Density
5V
J3
C
F
5V
J2
R4
R3
0.25pF
5V
J1
R
1M
F
V
= 1M • I
PD
OUT
R2
R1
BW = 400kHz
NOISE = 150µV
5V
RMS
MEASURED ON 100kHz
BANDWIDTH
–
1/2
C1
C2
C3
C4
I
PD
V
OUT
LTC6244HV
6244 TA02a
+
R5
4.99k
HAMAMATSU
LARGE AREA
PHOTODIODE
S1227-1010BQ
–5V
1
10
100
–5V
(kHz)
6244 TA02b
C1 TO C4: 4.7µF X7R
J1 TO J4: PHILIPS BF862 JFETS
R1 TO R4: 4.99k
C
= 3000pF
PD
RELATED PARTS
PART NUMBER
LTC1151
DESCRIPTION
15V Zero-Drift Op Amp
COMMENTS
Dual High Voltage Operation 18V
6nV/√Hz Noise, 15V Operation
2.7 Volt Operation, SOT-23
LT1792
Low Noise Precision JFET Op Amp
Zero-Drift Op Amp
LTC2050
LTC2051/LTC2052
LTC2054/LTC2055
LT6241/LT6242
Dual/Quad Zero-Drift Op Amp
Single/Dual Zero-Drift Op Amp
Dual/Quad, 18MHz CMOS Op Amps
Dual/Quad Version of LTC2050 in MS8/GN16 Packages
Micropower Version of the LTC2050/LTC2051 in SOT-23 and DD Packages
Low Noise, Rail-to-Rail
6244f
LT 0706 • PRINTED IN USA
24 LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
●
●
© LINEAR TECHNOLOGY CORPORATION 2006
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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LTC6246 - 180MHz, 1mA Power Efficient Single Rail-to-Rail I/O Op Amps; Package: SOT; Pins: 6; Temperature Range: -40°C to 125°C
Linear
LTC6246HS6#TRPBF
LTC6246 - 180MHz, 1mA Power Efficient Single Rail-to-Rail I/O Op Amps; Package: SOT; Pins: 6; Temperature Range: -40°C to 125°C
Linear
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