12

LT1169

© LINEAR TECHNOLOGY CORPORATION 1994

Linear Technology Corporation

1169fa LT/TP 0198 REV A 4K • PRINTED IN USA

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

LT1169 • TA08

TYPICAL OFFSET

≈ 0.8mV

1% TOLERANCES

= – 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

R2

237k

R6

249k

C4

330nF

5

6

1/2 LT1169

7

C3

10nF

R4

154k

R5

154k

8

1

15V

–15V

4

3

2

1/2 LT1169

1. ASSUME VOLTAGE NOISE OF LT1169 AND 51

Ω SOURCE RESISTOR = 6.1nV/√Hz

2. GAIN WITH n LT1169s IN PARALLEL = n

× 200

3. OUTPUT NOISE =

√n × 200 × 6.1nV/√Hz

4. INPUT REFERRED NOISE =

OUTPUT NOISE

=

6.1

nV/

√H

 z

n

× 200

√n

5. NOISE CURRENT AT INPUT INCREASES

√n TIMES

6. IF n = 5, GAIN = 1000, BANDWIDTH = 110kHz, RMS NOISE, DC TO 1MHz =

2.1

µV

= 1.0

µV

8

15V

–15V

4

8

15V

–15V

4

LT1169 • TA06

1.6k

91

Ω

7

6

5

3k

1.6k

91

Ω

1

2

3

–

+

A2

1/2 LT1169

–

+

1.6k

91

Ω

1

2

3

A1

1/2 LT1169

10k

7

5

6

1/2 LT1169

–

+

An

1/2 LT1169

3k

3k

OUTPUT

√5

Paralleling Amplifiers to Reduce Voltage Noise

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PART NUMBER

DESCRIPTION

COMMENTS

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4.5nV/

√Hz Voltage Noise

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Low Power Dual JFET Op Amp

3.0pA (Max) Input Bias Current