LT1792AIN8#PBF Datasheet LT1792ACS8#PBF, LT1792CS8#PBF, LT1792IN8#PBF | P10-P12

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LT1792

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I FOR ATIO

also increases the parasitic gate capacitance, which if left

unchecked, can result in increased overshoot and ring-

ing. When the feedback around the op amp is resistive

(R

F

), a pole will be created with R

F

, the source resistance

and capacitance (R

S

, C

S

), and the amplifier input capaci-

tance (C

IN

= 27pF). In low gain configurations and with

R

S

and R

F

in the kilohm range (Figure 5), this pole can

create excess phase shift and even oscillation. A small

capacitor (C

F

) in parallel with R

F

eliminates this problem.

With R

S

(C

S

+ C

IN

) = R

F

C

F

, the effect of the feedback pole

is completely removed.

Figure 5

–

+

1792 F05

OUTPUT

R

F

R

S

C

S

C

F

C

IN

1792 TA06

V

OUT

TYPICAL OFFSET ≈ 0.8mV

1% TOLERANCES

FOR V

IN

= 10V

P-P

, V

OUT

= –121dB AT f > 330Hz

= – 6dB AT f = 16.3Hz

LOWER RESISTOR VALUES WILL RESULT IN LOWER THERMAL NOISE AND LARGER CAPACITORS

R3

249k

C2

100nF

C1

33nF

R1

237k

V

IN

R2

237k

R6

249k

C4

330nF

3

2

–

+

LT1792

6

C3

10nF

R4

154k

R5

154k

7

15V

–15V

4

6

3

2

–

+

LT1792

10Hz Fourth Order Chebyshev Lowpass Filter (0.01dB Ripple)

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Accelerometer Amplifier with DC Servo

7

5V TO 15V

–5V TO –15V

4

1792 TA03

OUTPUT

R1

100M

C1

1250pF

R3

2k

C3

2µF

R2

18k

C2

2µF

2

3

R4

20M

–

+

LT1792

6

R5

20M

ACCELEROMETER

B & K MODEL 4381

OR EQUIVALENT

6

3

2

–

+

LT1792

R4C2 = R5C3 > R1 (1 + R2/R3) C1

OUTPUT = 0.8mV/pC* = 8.0mV/g**

DC OUTPUT ≤ 2.7mV

OUTPUT NOISE = 6nV/√Hz AT 1kHz

*PICOCOULOMBS

**g = EARTH’S GRAVITATIONAL CONSTANT

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LT1792

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Low Noise Light Sensor with DC Servo

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.

7

V

+

V

–

4

1792 TA05

R1

1M

C1

2pF

6

3

2

–

+

LT1792

R2C2 > C1R1

C

D

= PARASITIC PHOTODIODE CAPACITANCE

V

O

= 100mV/

µ

WATT FOR 200nm WAVE LENGTH

330mV/

µ

WATT FOR 633nm WAVE LENGTH

R5

1k

D2

1N914

2N3904

V

–

R4

1k

D1

1N914

R3

1k

6

3

2

–

+

LT1792

C2

0.022

µ

F

HAMAMATSU

S1336-5BK

OUTPUT

R2

100k

C

D

1. ASSUME VOLTAGE NOISE OF LT1792 AND 51Ω SOURCE RESISTOR = 4.3nV/√Hz

2. GAIN WITH n LT1792s IN PARALLEL = n × 200

3. OUTPUT NOISE = √n × 200 × 4.3nV/√Hz

4. INPUT REFERRED NOISE =

OUTPUT NOISE

=

4.3

nV/√Hz

n × 200

√

n

5. NOISE CURRENT AT INPUT INCREASES

√

n TIMES

7

15V

–15V

4

7

15V

–15V

4

1k

1792 TA04

6

2

3

1k

6

2

3

–

+

A2

LT1792

–

+

1k

51Ω

6

2

3

An

LT1792

10k

6

3

2

–

+

LT1792

–

+

A1

LT1792

1k

OUTPUT

Paralleling Amplifiers to Reduce Voltage Noise

12

LT1792

 LINEAR TECHNOLOGY CORPORATION 1999

1792f LTTP 0599 4K • PRINTED IN USA

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900

●

FAX: (408) 434-0507

●

www.linear-tech.com

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Light Balance Detection Circuit Unity-Gain Buffer with Extended

Load Capacitance Drive Capability

1792 TA07

V

OUT

= 1M × (I

1

– I

2

)

PD1

,

PD2 = HAMAMATSU S1336-5BK

WHEN EQUAL LIGHT ENTERS PHOTODIODES, V

OUT

< 3mV.

–

+

LT1792

R1

1M

C1

2pF TO 8pF

PD1

PD2

I

1

I

2

V

OUT

1792 TA08

V

OUT

–

+

LT1792

C1

V

IN

R2

1k

C

L

R1

33Ω

C1 = C

L

≤ 0.1µF

OUTPUT SHORT-CIRCUIT CURRENT

(∼ 30mA) WILL LIMIT THE RATE AT WHICH THE

VOLTAGE CAN CHANGE ACROSS LARGE CAPACITORS

I = C

()

dV

dt

RELATED PARTS

PART NUMBER DESCRIPTION COMMENTS

LT1113 Low Noise Dual JFET Op Amp Dual Version of LT1792, V

NOISE

= 4.5nV/√Hz

LT1169 Low Noise Dual JFET Op Amp Dual Version of LT1793, I

B

= 10pA, V

NOISE

= 6nV/√Hz

LT1793 Low Noise Single Op Amp Lower I

B

Version of LT1792, I

B

= 10pA, V

NOISE

= 6nV/√Hz

Dimensions in inches (millimeters) unless otherwise noted.

U

PACKAGE

D

E

SC

R

I

PTI

O

S8 Package

8-Lead Plastic Small Outline (Narrow 0.150)

(LTC DWG # 05-08-1610)

1

2

3

4

0.150 – 0.157**

(3.810 – 3.988)

8

7

6

5

0.189 – 0.197*

(4.801 – 5.004)

0.228 – 0.244

(5.791 – 6.197)

0.016 – 0.050

0.406 – 1.270

0.010 – 0.020

(0.254 – 0.508)

× 45°

0°– 8° TYP

0.008 – 0.010

(0.203 – 0.254)

SO8 0996

0.053 – 0.069

(1.346 – 1.752)

0.014 – 0.019

(0.355 – 0.483)

0.004 – 0.010

(0.101 – 0.254)

0.050

(1.270)

TYP

DIMENSION DOES NOT INCLUDE MOLD FLASH.

MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE

DIMENSION DOES NOT INCLUDE INTERLEAD FLASH.

INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE

*

**

N8 1197

0.100 ± 0.010

(2.540 ± 0.254)

0.065

(1.651)

TYP

0.045 – 0.065

(1.143 – 1.651)

0.130 ± 0.005

(3.302 ± 0.127)

0.020

(0.508)

MIN

0.018 ± 0.003

(0.457 ± 0.076)

0.125

(3.175)

MIN

12

3

4

876

5

0.255 ± 0.015*

(6.477 ± 0.381)

0.400*

(10.160)

MAX

0.009 – 0.015

(0.229 – 0.381)

0.300 – 0.325

(7.620 – 8.255)

0.325

+0.035

–0.015

+0.889

–0.381

8.255

()

*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.

MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)

N8 Package

8-Lead PDIP (Narrow 0.300)

(LTC DWG # 05-08-1510)

LT1792AIN8#PBF

LT1792AIN8#PBF

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