11

LT1792

S

APPLICATI

TYPICAL

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

4

1792 TA05

R1

1M

C1

2pF

6

3

2

LT1792

R2C2 > C1R1

330mV/

µWATT FOR 633nm WAVE LENGTH

R5

1k

D2

1N914

2N3904

R4

1k

D1

1N914

R3

1k

6

3

2

LT1792

C2

0.022

µF

HAMAMATSU

S1336-5BK

OUTPUT

R2

100k

1. ASSUME VOLTAGE NOISE OF LT1792 AND 51

Ω 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

1k

6

2

3

–

+

A2

LT1792

–

+

1k

51

Ω

51

Ω

51

Ω

6

2

3

An

LT1792

10k

6

3

2

LT1792

–

+

A1

LT1792

1k

1k

OUTPUT

Paralleling Amplifiers to Reduce Voltage Noise