Datasheet

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Ultra-Low Bias Current

Difet

OPERATIONAL AMPLIFIER

FEATURES

● ULTRA-LOW BIAS CURRENT: 100fA max

● LOW OFFSET: 2mV max

● LOW DRIFT: 10µV/°C max

● HIGH OPEN-LOOP GAIN: 94dB min

● LOW NOISE: 15nV/√Hz at 10kHz

● PLASTIC DIP AND SO PACKAGES

APPLICATIONS

● PHOTODETECTOR PREAMPS

● CHROMATOGRAPHY

● ELECTROMETER AMPLIFIERS

● MASS SPECTROMETERS

● pH PROBE AMPLIFIERS

● ION GAGE MEASUREMENT

DESCRIPTION

The OPA129 is an ultra-low bias current monolithic

operational amplifier offered in an 8-pin PDIP and

SO-8 package. Using advanced geometry

dielectrically-isolated FET (

Difet

) inputs, this monolithic

amplifier achieves a high performance level.

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 special pinout eliminates leakage current

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 packages,

specified for operation from –40°C to +85°C.

+In

Output

Noise-Free

Cascode

V–

V+

30kΩ 30kΩ

–In

Simplified Circuit

Substrate

OPA129

SBOS026A – JANUARY 1994 – REVISED APRIL 2007

www.ti.com

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of Texas Instruments

standard warranty. Production processing does not necessarily include

testing of all parameters.

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

Difet is a registered trademark of Texas Instruments.

All other trademarks are the property of their respective owners.

Summary of content (14 pages)

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OPA129 OPA OPA 129 129 SBOS026A – JANUARY 1994 – REVISED APRIL 2007 Ultra-Low Bias Current Difet® OPERATIONAL AMPLIFIER FEATURES APPLICATIONS ● ● ● ● ● ● ● ● ● ● ● ● ULTRA-LOW BIAS CURRENT: 100fA max LOW OFFSET: 2mV max LOW DRIFT: 10µV/°C max HIGH OPEN-LOOP GAIN: 94dB min LOW NOISE: 15nV/√Hz at 10kHz PLASTIC DIP AND SO PACKAGES PHOTODETECTOR PREAMPS CHROMATOGRAPHY ELECTROMETER AMPLIFIERS MASS SPECTROMETERS pH PROBE AMPLIFIERS ION GAGE MEASUREMENT Substrate DESCRIPTION 8 The OPA129 is an ultra-l
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SPECIFICATIONS ELECTRICAL At VS = ±15V and TA = +25°C, unless otherwise noted. Pin 8 connected to ground. OPA129PB, UB PARAMETER CONDITION MIN TYP OPA129P, U MAX MIN ±30 ±100 Doubles every 10°C TYP MAX UNITS * * ±250 fA INPUT BIAS CURRENT(1) vs Temperature VCM = 0V INPUT OFFSET CURRENT VCM = 0V ±30 VCM = 0V VS = ±5V to ±18V ±0.5 ±3 ±3 f = 10Hz f = 100Hz f = 1kHz f = 10kHz fB = 0.1Hz to 10Hz f = 10kHz 85 28 17 15 4 0.
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PACKAGE INFORMATION(1) ABSOLUTE MAXIMUM RATINGS Power Supply Voltage ...................................................................... ±18V Differential Input Voltage ............................................................ V– to V+ Input Voltage Range .................................................................... V– to V+ Storage Temperature Range ......................................... –40°C to +125°C Operating Temperature Range ......................................
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TYPICAL PERFORMANCE CURVES (Cont.) At TA = +25°C, +15VDC, unless otherwise noted.
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TYPICAL PERFORMANCE CURVES (Cont.) At TA = +25°C, +15VDC, unless otherwise noted. 3 3 2 2 1 Gain Bandwidth (MHz) 4 Slew Rate (V/µs) Gain Bandwidth (MHz) 4 1 0 –50 –25 0 25 50 75 100 6 2 4 +Slew –Slew 1 0 0 125 5 10 Ambient Temperature (°C) 15 20 Supply Voltage (±VCC) SUPPLY CURRENT vs TEMPERATURE OPEN-LOOP GAIN, PSR AND CMR vs TEMPERATURE 2.
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TYPICAL PERFORMANCE CURVES (CONT) TA = +25°C, +15VDC, unless otherwise noted. COMMON-MODE INPUT RANGE vs SUPPLY VOLTAGE BIAS CURRENT vs ADDITIONAL POWER DISSIPATION 100pA 10pA Bias Current (fA) Common-Mode Voltage (+V) 15 10 5 100 10 0 1 0 5 10 15 20 0 APPLICATIONS INFORMATION NON-STANDARD PINOUT The OPA129 uses a non-standard pinout to achieve lowest possible input bias current. The negative power supply is connected to pin 5—see Figure 1.
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CIRCUIT BOARD LAYOUT The OPA129 uses a new pinout for ultra low input bias current. Pin 1 and pin 4 have no internal connection. This allows ample circuit board space for a guard ring surrounding the op amp input pins—even with the tiny SO-8 surfacemount package. Figure 3 shows suggested circuit board layouts. The guard ring should be connected to pin 8 (substrate) as shown.
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE MATERIALS INFORMATION www.ti.com 14-Jul-2012 TAPE AND REEL INFORMATION *All dimensions are nominal Device OPA129UB/2K5 Package Package Pins Type Drawing SOIC D 8 SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) 2500 330.0 12.4 Pack Materials-Page 1 6.4 B0 (mm) K0 (mm) P1 (mm) 5.2 2.1 8.0 W Pin1 (mm) Quadrant 12.
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PACKAGE MATERIALS INFORMATION www.ti.com 14-Jul-2012 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) OPA129UB/2K5 SOIC D 8 2500 367.0 367.0 35.
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IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete.