®
OPA129
Ultra-Low Bias Current
Difet
®
OPERATIONAL AMPLIFIER
FEATURES
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ULTRA-LOW BIAS CURRENT: 100fA max
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q
q
q
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LOW OFFSET: 2mV max
LOW DRIFT: 10
µ
V/
°
C max
HIGH OPEN-LOOP GAIN: 94dB min
LOW NOISE: 15nV/
√
Hz at 10kHz
PLASTIC DIP and SOIC PACKAGE
APPLICATIONS
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PHOTODETECTOR PREAMP
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CHROMATOGRAPHY
ELECTROMETER AMPLIFIERS
MASS SPECTROMETER
pH PROBE AMPLIFIER
ION GAGE MEASUREMENT
DESCRIPTION
The OPA129 is an ultra-low bias current mono-
lithic operational amplifier offered in an 8-pin PDIP
and SO-8 package. Using advanced geometry
dielectrically-isolated FET (
Difet
®
) inputs, this mono-
lithic amplifier achieves a high performance level.
Substrate
8
7
V+
Difet
fabrication eliminates isolation-junction leakage
current—the main contributor to input bias current
with conventional monolithic FETs. This reduces
input bias current by a factor of 10 to 100. Very low
input bias current can be achieved without resorting to
small-geometry FETs or CMOS designs which can
suffer from much larger offset voltage, voltage noise,
drift, and poor power supply rejection.
The OPA129's special pinout eliminates leakage cur-
rent that occurs with other op amps. Pins 1 and 4 have
no internal connection, allowing circuit board guard
traces—even with the surface-mount package version.
OPA129 is available in 8-pin DIP and SO-8 packages,
specified for operation from –40°C to +85°C.
–In
2
3
+In
Noise-Free
Cascode
6
Output
30kΩ
30kΩ
5
V–
Simplified Circuit
Difet
®
Burr-Brown Corp.
International Airport Industrial Park • Mailing Address: PO Box 11400
Tel: (520) 746-1111 • Twx: 910-952-1111 • Cable: BBRCORP •
• Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd. • Tucson, AZ 85706
Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132
©
1994 Burr-Brown Corporation
PDS-1195A
Printed in U.S.A. July, 1994
BURR-BROWN [ BURR-BROWN CORPORATION ]
