Datasheet

20
LT1677
1677fa
LT 0306 REV A • PRINTED IN USA
© LINEAR TECHNOLOGY CORPORATION 2000
2-Wire Remote Geophone Preamp
RELATED PARTS
PART NUMBER DESCRIPTION COMMENTS
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LT1115 Ultralow Noise, Low distortion Audio Op Amp 0.002% THD, Max Noise 1.2nV/√Hz
LT1124/LT1125 Dual/Quad Low Noise, High Speed Precision Op Amps Similar to LT1007
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LT1226 Low Noise, Very High Speed Op Amp 1GHz, 2.6nV/√Hz, Gain of 25 Stable
LT1498/LT1499 10MHz, 5V/µs, Dual/Quad Rail-to-Rail Input and Output Op Amps Precision C-Load
TM
Stable
LT1792 Low Noise, Precision JFET Input Op Amp 4.2nV/√Hz, 10fA/√Hz
LT1793 Low Noise, Picoampere Bias Current Op Amp 6nV/√Hz, 1fA/√Hz, I
B
= 10pA Max
LT1806 Low Noise, 325MHz Rail-to-Rail Input and Output Op Amp 3.5nV/√Hz
LT1881/LT1882 Dual/Quad Rail-to-Rail Output Picoamp Input Precision Op Amps C
LOAD
to 1000pF, I
B
= 200pA Max
LT1884/LT1885 Dual/Quad Rail-to-Rail Output Picoamp Input Precision Op Amps 2.2MHz Bandwidth, 1.2V/µs SR
C-Load is a trademark of Linear Technology Corporation.
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone]
●
FAX: [phone]
●
www.linear-tech.com
TYPICAL APPLICATIO
U
This 2-wire remote Geophone preamp operates on a
current-loop principle and so has good noise immunity.
Quiescent current is ≈10mA for a V
OUT
of 2.5V. Excitation
will cause AC currents about this point of ~±4mA for a
V
OUT
of ~±1V max. The op amp is configured for a voltage
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.
–
+
LT1677
2
–
+
1677 TA04
4
7
6
3
R2
100k
R5
243Ω
C4
1000pF
Q1
2N3904
C2
0.1µF
R9
20Ω
12V
V
OUT
2.5V ±1V
R10
250Ω
R1
365Ω
R4
14k
R6
4.99k
R
R
V
–
V
+
C
3V
LT1431CZ
LINEAR
TECHNOLOGY
LM334Z
6mA
A
R3
16.2k
www.geospacecorp.com/default.htm
[phone]
GEOSPACE
GS-20DX
R
L
= 630Ω
GEOPHONE
C3
220µF
R8
11Ω
R7
24.9k
+
A
V
=
≅ 107
R2 + R3
||
R4
R1 + R
L
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