16

LT1677

1677i LT/TP 0200 4K • PRINTED IN USA

©LINEAR TECHNOLOGY CORPORATION 2000

2-Wire Remote Geophone Preamp

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PART NUMBER

DESCRIPTION

COMMENTS

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C-Load is a trademark of Linear Technology Corporation.

LT1677

2

–

+

1677 TA03

4

7

6

3

R2

100k

R5

243

Ω

C4

1000pF

Q1

2N3904

C2

0.1

µF

R9

20

Ω

12V

2.5V

±1V

R10

250

Ω

R1

150

Ω

R4

14k

R6

4.99k

R

R

C

3V

LT1431CZ

LINEAR

TECHNOLOGY

LM334Z

6mA

A

R3

16.2k

GEOSOURCE

MD-105

GEOPHONE

C3

220

µF

R8

11

Ω

R7

24.9k

+

≅ 107

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

TYPICAL APPLICATIO

This 2-wire remote Geophone preamp operates on a

current-loop principle and so has good noise immunity.

Quiescent current is

will cause AC currents about this point of ~

±4mA for a

gain of ~107. Components R5 and Q1 convert the voltage

into a current for transmission back to R10, which con-

verts it into a voltage again. The LM334 and 2N3904 are

not temperature compensated so the DC output contains

temperature information.