LT1223CJ8_技术文档

LT1223

100MHz Current

Feedback Amplifier

U

DESCRIPTIO

EATURE

S

F

■

100MHz Bandwidth at A_V= 1

1000V/µs Slew Rate

Wide Supply Range: ±5V to ±15V

1mV Input Offset Voltage

1µA Input Bias Current

5MΩ Input Resistance

75ns Settling Time to 0.1%

50mA Output Current

6mA Quiescent Current

The LT1223 is a 100MHz current feedback amplifier with

very good DC characteristics. The LT1223’s high slew

rate,1000V/µs,widesupplyrange,±15V,andlargeoutput

drive, ±50mA, make it ideal for driving analog signals over

double- terminated cables. The current feedback amplifier

hashighgainbandwidthathighgains,unlikeconventional

op amps.

The LT1223 comes in the industry standard pinout and

can upgrade the performance of many older products.

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The LT1223 is manufactured on Linear Technology’s

proprietary complementary bipolar process.

■

Video Amplifiers

Buffers

IF and RF Amplification

Cable Drivers

8-, 10-, 12-Bit Data Acquisition Systems

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TYPICAL APPLICATI

Video Cable Driver

Voltage Gain vs Frequency

60

100MHz GAIN

BANDWIDTH

+

–

V

IN

50

40

75Ω

–

R

G

R

G

R

G

R

G

R

G

= 10

= 33

= 110

= 470

= ∞

LT1223

1k

R_G

30

75Ω

CABLE

R

F

1k

20

10

V

OUT

R

0

G

1k

75Ω

–10

–20

100k

1M

10M

FREQUENCY (Hz)

100M

1G

R

F

A

= 1 +

V

R

G

LT1223 • TPC01

AT AMPLIFIER OUTPUT.

6dB LESS AT V

.

OUT

LT1223 • TA02

1

LT1223

W W W

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ABSOLUTE AXI U RATI GS

PACKAGE RDER I FOR ATIO

Supply Voltage ...................................................... ±18V

Differential Input Voltage ......................................... ±5V

Input Voltage ............................ Equal to Supply Voltage

Output Short Circuit Duration (Note 1) .........Continuous

Operating Temperature Range

LT1223M........................................ –55°C to 125°C

LT1223C................................................ 0°C to 70°C

Storage Temperature Range ................. –65°C to 150°C

Junction Temperature Plastic Package........... 150°C

Junction Temperature Ceramic Package ........ 175°C

Lead Temperature (Soldering, 10 sec.)................. 300°C

TOP VIEW

ORDER PART

NUMBER

NULL

–IN

1

2

3

4

8

7

6

5

SHUTDOWN

+

V

LT1223MJ8

LT1223CJ8

LT1223CN8

LT1223CS8

+IN

OUT

–

V

NULL

J8 PACKAGE

N8 PACKAGE

8-LEAD CERAMIC DIP 8-LEAD PLASTIC DIP

S8 PACKAGE

8-LEAD PLASTIC SOIC

S8 PART MARKING

1223

LT1223 • POI01

T_{J MAX}= 175°C, θ_JA= 100°C/W(J8)

_{J MAX}= 150°C, θ_JA= 100°C/W(N8)

_{J MAX}= 150°C, θ_JA= 150°C/W(S8)

T

V = ± 15V, T = 25°C, unless otherwise noted.

ELECTRICAL CHARACTERISTICS

S

A

LT1223M/C

TYP

SYMBOL

PARAMETER

CONDITIONS

MIN

MAX

±3

UNITS

mV

µA

V

OS

Input Offset Voltage

V

CM

V

CM

V

CM

= 0V

±1

3.3

2.2

10

I +

IN

Noninverting Input Current

Inverting Input Current

±3

I –

IN

±3

µA

e

n

Input Noise Voltage Density

Input Noise Current Density

Input Resistance

f = 1kHz, R = 1k, R = 10Ω

nV/√Hz

pA/√Hz

MΩ

pF

F

G

i

n

f = 1kHz, R = 1k, R = 10Ω

F G

R

IN

V

IN

= ±10V

1

C

IN

Input Capacitance

1.5

±12

63

Input Voltage Range

±10

V

CMRR

PSRR

Common-Mode Rejection Ratio

Inverting Input Current Common-Mode Rejection

Power Supply Rejection Ratio

Noninverting Input Current Power Supply Rejection

Inverting Input Current Power Supply Rejection

Large Signal Voltage Gain

V

= ±10V

56

dB

CM

30

100

nA/V

dB

CM

V = ±4.5V to ±18V

S

68

80

V = ±4.5V to ±18V

S

12

100

500

nA/V

dB

V = ±4.5V to ±18V

S

60

A

V

R

LOAD

R

LOAD

R

LOAD

R

LOAD

= 400Ω, V

= 200Ω

= ±10V

70

1.5

±10

50

89

OUT

R

OL

Transresistance, ∆V /∆I –

5

MΩ

V

OUT IN

V

Maximum Output Voltage Swing

Maximum Output Current

Slew Rate

±12

60

OUT

I

= 200Ω

mA

V/µs

MHz

ns

SR

R = 1.5k, R = 1.5k, (Note 2)

800

1300

100

6.0

5

F

G

BW

Bandwidth

R = 1k, R = 1k, V

= 100mV

OUT

F

G

t

Rise Time

R = 1.5k, R = 1.5k, V

= 1V

r

F

G

OUT

Propagation Delay

Overshoot

R = 1.5k, R = 1.5k, V

ns

PD

F

G

R = 1.5k, R = 1.5k, V

%

F

G

t

Settling Time, 0.1%

Differential Gain

R = 1k, R = 1k, V = 10V

OUT

75

ns

s

F

G

R = 1k, R = 1k, R = 150Ω

0.02

0.12

35

%

F

G

L

Differential Phase

Open-Loop Output Resistance

Supply Current

R = 1k, R = 1k, R = 150Ω

Deg

Ω

F

G

L

R

V

= 0, I

= 0

OUT

I

= 0V

IN

6

10

4

mA

S

Supply Current, Shutdown

Pin 8 Current = 200µA

2

LT1223

V = ± 15V, V_CM= 0V, 0°C ≤ T_A≤ 70°C, unless otherwise noted.

ELECTRICAL CHARACTERISTICS

S

LT1223C

SYMBOL

PARAMETER

CONDITIONS

MIN

±1

1

TYP

±3

10

±12

63

30

80

12

60

89

5

MAX

UNITS

V

OS

Input Offset Voltage

V

= 0V

●

mV

µA

CM

I +

IN

Noninverting Input Current

I –

IN

Inverting Input Current

R

IN

Input Resistance

= ±10V

MΩ

V

IN

Input Voltage Range

±10

56

CMRR

PSRR

Common-Mode Rejection Ratio

Inverting Input Current Common-Mode Rejection

Power Supply Rejection Ratio

Noninverting Input Current Power Supply Rejection

Inverting Input Current Power Supply Rejection

Large-Signal Voltage Gain

V

= ±10V

dB

CM

100

nA/V

dB

CM

V = ±4.5V to ±18V

S

68

V = ±4.5V to ±18V

100

500

nA/V

dB

S

V = ±4.5V to ±18V

S

A

V

R

= 400Ω, V

= 200Ω

= ±10V

70

1.5

±10

50

LOAD

OUT

R

Transresistance, ∆V /∆I –

MΩ

V

OL

OUT

S

OUT IN

V

Maximum Output Voltage Swing

Maximum Output Current

Supply Current

±12

60

6

I

= 200Ω

mA

V

IN

= 0V

10

4

Supply Current, Shutdown

Pin 8 Current = 200µA

2

V = ± 15V, V_CM= 0V, –55°C ≤ T_A≤ 125°C, unless otherwise noted.

ELECTRICAL CHARACTERISTICS

S

LT1223M

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

±1

10

±12

63

30

80

12

60

89

5

MAX

±5

UNITS

mV

µA

V

OS

Input Offset Voltage

V

= 0V

●

CM

I +

IN

Noninverting Input Current

±5

I –

IN

Inverting Input Current

±10

µA

R

IN

Input Resistance

= ±10V

1

MΩ

V

IN

Input Voltage Range

±10

56

CMRR

PSRR

Common-Mode Rejection Ratio

Inverting Input Current Common-Mode Rejection

Power Supply Rejection Ratio

Noninverting Input Current Power Supply Rejection

Inverting Input Current Power Supply Rejection

Large-Signal Voltage Gain

V

= ±10V

dB

CM

100

nA/V

dB

CM

V = ±4.5V to ±15V

S

68

V = ±4.5V to ±15V

S

200

500

nA/V

dB

V = ±4.5V to ±15V

S

A

V

R

LOAD

R

LOAD

R

LOAD

R

LOAD

= 400Ω, V

= 200Ω

= ±10V

70

1.5

±7

35

OUT

R

Transresistance, ∆V /∆I –

MΩ

V

OL

OUT

S

OUT IN

V

Maximum Output Voltage Swing

Maximum Output Current

Supply Current

±12

60

6

I

= 200Ω

mA

V

IN

= 0V

10

4

Supply Current, Shutdown

Pin 8 Current = 200µA

2

The

●

denotes the specifications which apply over the full operating

temperature range.

Note 1: A heat sink may be required.

Note 2: Noninverting operation, V

= ±10V, measured at ±5V.

OUT

3

LT1223

TYPICAL PERFOR A CE CHARACTERISTICS

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Supply Current vs Supply Voltage,

Supply Current vs Supply Voltage

(Shutdown)

Output Short Circuit-Current vs

Temperature

V

_IN= 0 (Operating)

10

8

4

3

2

1

0

100

90

80

70

60

50

40

PIN 8 = 0V

125°C

25°C

6

125°C

–55°C

4

–55°C

30

20

2

0

10

0

2

4

6

8

10 12 14 16 18 20

–50 –25

0

25

50

75 100 125

0

2

4

6

8

10 12 14 16 18 20

SUPPLY VOLTAGE (±V)

CASE TEMPERATURE (°C)

SUPPLY VOLTAGE (±V)

LT1223 • TPC03

LT1223 • TPC04

LT1223 • TPC02

Input Common-Mode Limit vs

Temperature

+I_Bvs Common-Mode Voltage

–I_Bvs Common-Mode Voltage

10

8

V+

–1

5

4

V

= ±15V

S

V

= ±15V

S

125°C

V

= 15V

6

4

2

3

2

1

S

–2

–3

–4

+4

+3

+2

–55°C

25°C

V = 5V

S

–55°C

25°C

0

125°C

–2

–1

–4

–6

–2

–3

–4

–5

V = –15V

S

V = –5V

S

+1

V–

–8

–10

–50 –25

0

25

50

75 100 125

–15 –10

–5

0

5

10

15

–15 –10

–5

0

5

10

15

TEMPERATURE (°C)

COMMON MODE VOLTAGE (V)

LT1223 • TPC05

LT1223 • TPC07

LT1223 • TPC06

Output Voltage Swing vs

Load Resistor

Output Voltage Swing vs

Supply Voltage

V_OSvs Common-Mode Voltage

20

15

20

15

20

15

V

S

= ±15V

±

= 15V

V

S

125°C

25°C

10

5

10

5

25°C, –55°C

10

–55°C

5

125°C

0

25°C

–5

25°C

–5

–10

–15

–20

–55°C

–10

–15

–20

–10

–15

–20

25°C, –55°C

125°C

–15 –10

–5

0

5

10

15

100

1000

LOAD RESISTOR (Ω)

10000

0

2

4

6

8

10 12 14 16 18 20

COMMON MODE VOLTAGE (V)

SUPPLY VOLTAGE (±V)

LT1223 • TPC08

LT1223 • TPC09

LT1223 • TPC10

4

LT1223

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TYPICAL PERFOR A CE CHARACTERISTICS

–3dB Bandwidth vs

Feedback Resistor

–3dB Bandwidth vs

Supply Voltage

Minimum Feedback Resistor vs

Voltage Gain

100

90

80

70

60

50

40

1000

900

800

700

600

500

400

300

200

100

90

80

70

60

50

40

A

R

= 2; R = R

F

R = R

G

S

±

F

V

L

G

V

=

15V

V

L

S

L

Ω

±

15V

= 100 ; V

=

A

R

= 2

= 100

= 25°C

R

= 100

NO CAPACITIVE LOAD

Ω

T

A

R = 750

F

R = 1k

F

0dB PEAKING

2dB PEAKING

R = 1.5k

F

30

20

30

20

R = 2k

F

10

0

10

0

1

2

3

0

10

20

30

40

50

60

0

5

10

15

FEEDBACK RESISTOR (kΩ)

VOLTAGE GAIN (V/V)

SUPPLY VOLTAGE (±V)

LT1223 • TPC11

LT1223 • TPC13

LT1223 • TPC12

Maximum Capacitive Load vs

Feedback Resistor

Open-Loop Voltage Gain vs

Load Resistor

Transimpedance vs Load Resistor

10

9

100

90

10k

1k

25°C

V

O

= ±15V

= ±10V

A

R

= 2; R = R

F G

S

V

L

V

±

= 15V

= 100; V

S

8

7

6

5

4

3

2

1

0

PEAKING < 5dB

–55°C

80

25°C

125°C

–55°C

70

60

125°C

100

10

50

40

V = ±15V

O

S

V = ±10V

100

1000

LOAD RESISTOR (Ω)

10000

100

1000

LOAD RESISTOR (Ω)

10000

0

1

2

3

FEEDBACK RESISTOR (kΩ)

LT1223 • TPC16

LT1223 • TPC15

LT1223 • TPC14

Spot Noise Voltage and Current vs

Frequency

Power Supply Rejection vs

Frequency

Output Impedance vs Frequency

80

60

40

1000

100

10

100

10

1

V

= ±15V

V = ±15V

S

R = 1k

F

POSITIVE

–i

n

R

= R = 3k

G

F

NEGATIVE

R

= R = 1k

G

e

F

n

20

0

0.1

+i

n

0.01

1

10k

100k

1M

10M

100M

10

100

1k

10k

100k

1M

10M

100M

FREQUENCY (Hz)

LT1223 • TPC18

LT1223 • TPC17

LT1223 • TPC19

5

LT1223

TYPICAL PERFOR A CE CHARACTERISTICS

U W

Voltage Gain and Phase vs

Total Harmonic Distortion vs

2nd and 3rd Harmonic

Distortion vs Frequency

Frequency

20

15

225

180

0.1

–20

–30

–40

–50

–60

–70

V

= ±15V

V

= ±15V

S

F

S

V

= ±15V

S

2ND

3RD

R = R = 1k

V

= 7V

RMS

G

O

R

V

= 2V

P-P

O

= 400Ω

10

5

135

90

R

A

= 100

= 1k

L

F

L

F

GAIN

= R =1k

G

= 10dB

R = 100Ω

R

≥ 1k

V

L

0

–5

45

PHASE

0.01

0

R

≥ 1k

L

–10

–15

–20

–25

–30

–45

–90

–135

–180

–225

R

= 100Ω

L

THD

0.001

1M

10M

100M

1G

10

100

1k

FREQUENCY (Hz)

10k

100k

1

10

100

FREQUENCY (Hz)

FREQUENCY (MHz)

LT1223 • TPC21

LT1223 • TPC20

LT1223 • TPC22

Noninverting Amplifier Settling

Time to 10mV vs Output Step

Noninverting Amplifier Settling

Time to 1mV vs Output Step

Inverting Amplifier Settling

Time vs Output Step

10

8

10

8

10

8

A

R

V

= +1

A

R

V

= +1

V

F

A

R

V

= –1

V

F

V

F

TO 10mV

= 1k

= ±15V

= 1k

= ±15V

= 1k

S

= ±15V

= 1k

6

TO 10mV

6

S

R

TO 1mV

R

L

TO 1mV

4

2

0

–2

–4

–6

–4

–6

–4

–6

TO 1mV

TO 10mV

20

TO 1mV

TO 10mV

60

–8

–10

0

20

40

80

100

0

1

2

0

40

60

80

100

SETTLING TIME (ns)

SETTLING TIME (µs)

SETTLING TIME (ns)

LT1223 • TPC23

LT1223 • TPC24

LT1223 • TPC25

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Current Feedback Basics

does in a voltage feedback op amp, the closed-loop

bandwidth does not change. This is because the equiva-

lent gain bandwidth product of the current feedback am-

plifier is set by the Thevenin equivalent resistance at the

inverting input and the internal compensation capacitor.

By keeping R_Fconstant and changing the gain with R_G, the

Thevenin resistance changes by the same amount as the

change in gain. As a result, the net closed-loop bandwidth

of the LT1223 remains the same for various closed-loop

gains.

The small-signal bandwidth of the LT1223, like all current

feedback amplifiers, isn’t a straight inverse function of the

closed-loop gain. This is because the feedback resistors

determine the amount of current driving the amplifier’s

internal compensation capacitor. In fact, the amplifier’s

feedback resistor (R_F) from output to inverting input

workswithinternaljunctioncapacitancesoftheLT1223to

set the closed-loop bandwidth.

Eventhoughthegainsetresistor(R_G)frominvertinginput

to ground works with R_Fto set the voltage gain just like it

6

LT1223

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The curve on the first page shows the LT1223 voltage gain

versusfrequencywhiledriving100Ω,forfivegainsettings

from 1 to 100. The feedback resistor is a constant 1k and

the gain resistor is varied from infinity to 10Ω. Shown for

comparison is a plot of the fixed 100MHz gain bandwidth

limitation that a voltage feedback amplifier would have. It

is obvious that for gains greater than one, the LT1223

provides 3 to 20 times more bandwidth. It is also evident

thatsecondorder effects reduce thebandwidthsomewhat

at the higher gain settings.

is not necessary to use equal value split supplies, how-

ever, the offset voltage will degrade about 350µV per volt

of mismatch. The internal compensation capacitor de-

creases with increasing supply voltage. The –3dB Band-

width versus Supply Voltage curve shows how this affects

the bandwidth for various feedback resistors. Generally,

the bandwidth at ±5V supplies is about half the value it is

at ±15V supplies for a given feedback resistor.

The LT1223 is very stable even with minimal supply

bypassing, however, the transient response will suffer if

thesupplyrings.Itisrecommendedforgoodslewrateand

settling time that 4.7µF tantalum capacitors be placed

within 0.5 inches of the supply pins.

Feedback Resistor Selection

Because the feedback resistor determines the compensa-

tion of the LT1223, bandwidth and transient response can

be optimized for almost every application. To increase the

bandwidth when using higher gains, the feedback resistor

(and gain resistor) can be reduced from the nominal 1k

value. The Minimum Feedback Resistor versus Voltage

Gain curve shows the values to use for ±15V supplies.

Larger feedback resistors can also be used to slow down

the LT1223 as shown in the –3dB Bandwidth versus

Feedback Resistor curve.

Input Range

The noninverting input of the LT1223 looks like a 10M

resistor in parallel with a 3pF capacitor until the common

mode range is exceeded. The input impedance drops

somewhat and the input current rises to about 10µA when

the input comes too close to the supplies. Eventually,

when the input exceeds the supply by one diode drop, the

base collector junction of the input transistor forward

biases and the input current rises dramatically. The input

current should be limited to 10mA when exceeding the

supplies. The amplifier will recover quickly when the input

is returned to its normal common mode range unless the

input was over 500mV beyond the supplies, then it will

take an extra 100ns.

Capacitive Loads

The LT1223 can be isolated from capacitive loads with a

small resistor (10Ω to 20Ω) or it can drive the capacitive

load directly if the feedback resistor is increased. Both

techniques lower the amplifier’s bandwidth about the

same amount. The advantage of resistive isolation is that

the bandwidth is only reduced when the capacitive load is

present. The disadvantage of resistor isolation is that

resistive loading causes gain errors. Because the DC

accuracy is not degraded with resistive loading, the de-

sired way of driving capacitive loads, such as flash con-

verters, istoincreasethefeedbackresistor. TheMaximum

Capacitive Load versus Feedback Resistor curve shows

the value of feedback resistor and capacitive load that

gives 5dB of peaking. For less peaking, use a larger

feedback resistor.

Offset Adjust

Output offset voltage is equal to the input offset voltage

times the gain plus the inverting input bias current times

the feedback resistor. For low gain applications (3 or less)

a 10kΩ pot connected to pins 1 and 5 with wiper to V⁺will

trim the inverting input current (±10µA) to null the output;

it does not change the offset voltage very much. If the

LT1223 is used in a high gain application, where input

offset voltage is the dominate error, it can be nulled by

pullingapproximately100µAfrompin1or5.Theeasyway

to do this is to use a 10kΩ pot between pin 1 and 5 with a

150k resistor from the wiper to ground for 15V supply

applications. Use a 47k resistor when operating on a 5V

supply.

Power Supplies

The LT1223 may be operated with single or split supplies

as low as ±4V (8V total) to as high as ±18V (36V total). It

7

LT1223

PPLICATI

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Shutdown

Output Slew Rate of 500V/µs

Pin 8 activates a shutdown control function. Pulling more

than200µAfrompin8dropsthesupplycurrenttolessthan

3mA, and puts the output into a high impedance state. The

easy way to force shutdown is to ground pin 8, using an

opencollector(drain)logicstage.Aninternalresistorlimits

current, allowingdirectinterfacingwithnoadditionalparts.

When pin 8 is open, the LT1223 operates normally.

Slew Rate

The slew rate of a current feedback amplifier is not inde-

pendent of the amplifier gain configuration the way it is in

a traditional op amp. This is because the input stage and

the output stage both have slew rate limitations. Inverting

amplifiers do not slew the input and are therefore limited

only by the output stage. High gain, noninverting amplifi-

ers are similar. The input stage slew rate of the LT1223 is

about 350V/µs before it becomes nonlinear and is en-

hanced by the normally reverse-biased emitters on the

input transistors. The output slew rate depends on the size

of the feedback resistors. The peak output slew rate is

about 2000V/µs with a 1k feedback resistor and drops

proportionally for larger values. At an output slew rate of

1000V/µs or more, the transistors in the “mirror circuits”

will begin to saturate due to the large feedback currents.

Thiscausestheoutputtohaveslewinducedovershootand

is somewhat unusual looking; it is in no way harmful or

dangerous to the device. The photos show the LT1223 in

a noninverting gain of three (R_F= 1k, R_G= 500Ω) with a

20V peak-to-peak output slewing at 500V/µs, 1000V/µs

and 2000V/µs.

Output Slew Rate of 1000V/µs

Output Slew Rate at 2000V/µs Shows Aberrations (See Text)

Settling Time

The Inverting Amplifier Settling Time versus Output Step

curve shows that the LT1223 will settle to within 1mV of

final value in less than 100ns for all output changes of 10V

or less. When operated as an inverting amplifier there is

less than 500µV of thermal settling in the amplifier.

However, when operating the LT1223 as a noninverting

amplifier, there is an additional thermal settling compo-

nent that is about 200µV for every volt of input common

mode change. So a noninverting gain of one amplifier will

8

LT1223

O U

W

U

PPLICATI

A

S I FOR ATIO

have about 2.5mV thermal tail on a 10V step. Unfortu-

nately, reducing the input signal and increasing the gain

always results in a thermal tail of about the same amount

for a given output step. For this reason we show separate

graphs of 10mV and 1mV non-inverting amplifier settling

times. Just as the bandwidth of the LT1223 is fairly

constant for various closed-loop gains, the settling time

remains constant as well.

Accurate Bandwidth Limiting The LT1223

It is very common to limit the bandwidth of an op amp by

putting a small capacitor in parallel with R_F. DO NOT PUT

A SMALL CAPACITOR FROM THE INVERTING INPUT OF

ACURRENTFEEDBACKAMPLIFIERTOANYWHERE ELSE,

ESPECIALLY NOT TO THE OUTPUT. The capacitor on the

inverting input will cause peaking or oscillations. If you

needtolimitthebandwidthofacurrentfeedbackamplifier,

use a resistor and capacitor at the noninverting input (R1

& C1). This technique will also cancel (to a degree) the

peakingcausedbystraycapacitanceattheinvertinginput.

Unfortunately, this will not limit the output noise the way

it does for the op amp.

Adjustable Gain Amplifier

TomakeavariablegainamplifierwiththeLT1223,varythe

value of R_G. The implementation of R_Gcan be a pot, a light

controlled resistor, a FET, or any other low capacitance

variable resistor. The value of R_Fshould not be varied to

change the gain. If R_Fis changed, then the bandwidth will

be reduced at maximum gain and the circuit will oscillate

when R_Fis very small.

R1

V

+

–

IN

LT1223

V

OUT

C1

V

+

–

IN

R

F

LT1223

V

OUT

R

G

R1 = 300Ω

C1 = 100pF

BW = 5MHz

R

F

LT1223 • TA05

R

G

LT1223 • TA03

Current Feedback Amplifier Integrator

Adjustable Bandwidth Amplifier

Since we remember that the inverting input wants to see

a resistor, we can add one to the standard integrator

circuit. Thisgeneratesanewsummingnodewherewecan

apply capacitive feedback. The LT1223 integrator has

excellentlargesignalcapabilityandaccuratephaseshiftat

high frequencies.

Because the resistance at the inverting input determines

the bandwidth of the LT1223, an adjustable bandwidth

circuit can be made easily. The gain is set as before with

R_Fand R_G; the bandwidth is maximum when the variable

resistor is at a minimum.

V

+

–

IN

+

LT1223

V

OUT

LT1223

V

OUT

V

OUT

1

I

=

–

sC R

IN

I

5k

R

F

R

F

G

1k

C

I

R

I

V

IN

LT1223 • TA04

LT1223 • TA06

9

LT1223

PPLICATI

O U

W

U

A

S I FOR ATIO

inverting input (A1) senses the shield and the non-invert-

ing input (A2) senses the center conductor. Since this

amplifier does not load the cable (take care to minimize

stray capacitance) and it rejects common mode hum and

noise, several amplifiers can sense the signal with only

one termination at the end of the cable. The design

equations are simple. Just select the gain you need (it

should be two or more) and the value of the feedback

resistor (typically 1k) and calculate R_G1and R_G2. The gain

canbetweakedwithR_G2andtheCMRRwithR_G1ifneeded.

The bandwidth of the noninverting input signal is not

reduced by the presence of the other amplifier, however,

the inverting input signal bandwidth is reduced since it

passes two amplifiers. The CMRR is good at high frequen-

cies because the bandwidth of the amplifiers are about the

same even though they do not necessarily operate at the

same gain.

Summing Amplifier (DC Accurate)

Thesummingamplifieriseasilymadebyaddingadditional

inputs to the basic inverting amplifier configuration. The

LT1223 has no I_OSspec because there is no correlation

betweenthetwoinputbiascurrents. Therefore, wewillnot

improve the DC accuracy of the inverting amplifier by

putting in the extra resistor in the noninverting input.

+

LT1223

V

OUT

R

1

2

G

V

–

I1

I2

R

F

G

•

V

R

•

I1

I2

In

V

= –R

F

+

•

OUT

(

)

R

G1

G2

Gn

n

G

V

In

LT1223 • TA07

R

F2

1k

G1

F1

G2

1k

Difference Amplifier

The LT1223 difference amplifier delivers excellent

performance if the source impedance is very low. This is

because the common mode input resistance is only equal

to R_F+ R_G.

–

+

–

+

A1

LT1223

A2

LT1223

V

OUT

V

–

V +

IN

R

(R –50)

F

G

+

–

)

OPTIONAL TRIM

FOR CMRR

V

R

= G (V – V

IN IN

V

OUT

1

R

F2

G – 1

100

= R ; R = (G – 1) R ; R =

F2 G1

F1

F2 G2

TRIM GAIN (G) WITH R ; TRIM CMRR WITH R

LT1223 • TA09

G2

G1

+

LT1223

V

OUT

R

G

Cable Driver

–

V

2

The cable driver circuit is shown on the front page. When

driving a cable it is important to properly terminate both

ends if even modest high frequency performance is

required. The additional advantage of this is that it isolates

the capacitive load of the cable from the amplifier so it can

operate at maximum bandwidth.

R

F

V

=

(V – V )

R

F

1

2

OUT

R

G

LT1223 • TA08

Video Instrumentation Amplifier

This instrumentation amplifier uses two LT1223s to in-

crease the input resistance to well over 1M. This makes an

excellent “loop through” or cable sensing amplifier if the

10

LT1223

U

O

TYPICAL APPLICATI

150mA Output Current Video Amp

75Ω

+

V

+

V

20Ω

V

+

–

IN

BIAS

OUT

IN

2k

LT1223

LT1010

–

V

2k

R

= 2k TO STABILIZE CIRCUIT

DIFFERENTIAL GAIN = 1%

DIFFERENTIAL PHASE = 1°

f

75Ω

LT1223 • TA10

W

SI PLIFIED SCHE ATIC

7

15k

1

5

BIAS

10k

8

3

6

2

BIAS

4

LT1223 • TA01

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-

tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.

11

LT1223

U

Dimensions in inches (millimeters) unless otherwise noted.

PACKAGE DESCRIPTIO

J8 Package

8-Lead Ceramic DIP

0.405

(10.287)

MAX

0.005

(0.127)

MIN

0.200

(5.080)

MAX

0.290 – 0.320

(7.366 – 8.128)

6

5

4

8

7

0.015 – 0.060

(0.381 – 1.524)

0.025

(0.635)

RAD TYP

0.220 – 0.310

(5.588 – 7.874)

0.008 – 0.018

0° – 15°

(0.203 – 0.460)

1

2

3

0.055

(1.397)

MAX

0.038 – 0.068

(0.965 – 1.727)

0.385 ± 0.025

(9.779 ± 0.635)

0.125

3.175

MIN

0.100 ± 0.010

0.014 – 0.026

(2.540 ± 0.254)

(0.360 – 0.660)

J8 0392

N8 Package

8-Lead Plastic DIP

0.400

(10.160)

MAX

0.130 ± 0.005

0.300 – 0.320

0.045 – 0.065

(3.302 ± 0.127)

(1.143 – 1.651)

(7.620 – 8.128)

8

1

7

6

5

4

0.065

(1.651)

TYP

0.250 ± 0.010

(6.350 ± 0.254)

0.009 – 0.015

(0.229 – 0.381)

0.125

0.020

(0.508)

MIN

(3.175)

MIN

+0.025

–0.015

2

3

0.045 ± 0.015

(1.143 ± 0.381)

0.100 ± 0.010

(2.540 ± 0.254)

0.325

+0.635

8.255

(

)

–0.381

0.018 ± 0.003

(0.457 ± 0.076)

N8 0392

S8 Package

8-Lead Plastic SOIC

0.189 – 0.197

(4.801 – 5.004)

0.010 – 0.020

(0.254 – 0.508)

7

5

8

6

× 45°

0.053 – 0.069

(1.346 – 1.752)

0.004 – 0.010

(0.101 – 0.254)

0.008 – 0.010

(0.203 – 0.254)

0.228 – 0.244

0.150 – 0.157

(5.791 – 6.197)

(3.810 – 3.988)

0.016 – 0.050

0.406 – 1.270

0.050

(1.270)

BSC

0.014 – 0.019

(0.355 – 0.483)

0°– 8° TYP

SO8 0392

1

3

4

2

LT/GP 1092 5K REV A

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7487

12

●

LINEAR TECHNOLOGY CORPORATION 1992

(408) 432-1900 FAX: (408) 434-0507 TELEX: 499-3977


型号：	LT1223CJ8
厂家：	Linear
描述：	100MHz Current Feedback Amplifier 100MHz的电流反馈放大器器放大器
文件：	总12页 (文件大小：292K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LT1223CJ8 [Linear]

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