Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsLinear ICsLinear IC - Op-amp Multi-purpose TO 99 8

Difet

Electrometer-Grade

OPERATIONAL AMPLIFIER

OPA128

Noise-Free

Cascode

Ω1k

Trim

+In

–In

Case (Guard)

Output

OPA128 Sim

lified Circuit

–V

28kΩ

Ω1k

2kΩ 2kΩ

Trim

28kΩ

FEATURES

● ULTRA-LOW BIAS CURRENT: 75fA max

● LOW OFFSET: 500µV max

● LOW DRIFT: 5µV/°C max

● HIGH OPEN-LOOP GAIN: 110dB min

● HIGH COMMON-MODE REJECTION:

90dB min

● IMPROVED REPLACEMENT FOR AD515

AND AD549

DESCRIPTION

The OPA128 is an ultra-low bias current monolithic

operational amplifier. Using advanced geometry

dielectrically-isolated FET (

Difet

) inputs, this mono-

lithic amplifier achieves a performance level exceed-

ing even the best hybrid electrometer amplifiers.

Laser-trimmed thin-film resistors give outstanding volt-

age offset and drift performance.

A noise-free cascode and low-noise processing give

the OPA128 excellent low-level signal handling capa-

bilities. Flicker noise is very low.

The OPA128 is an improved pin-for-pin replacement

for the AD515.

Difet

Burr-Brown Corp.

APPLICATIONS

● ELECTROMETER

● MASS SPECTROMETER

● CHROMATOGRAPH

● ION GAUGE

● PHOTODETECTOR

● RADIATION-HARD EQUIPMENT

1986 Burr-Brown Corporation PDS-653E Printed in U.S.A. May, 1995

International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111 • Twx: 910-952-1111

Internet: http://www.burr-brown.com/ • FAXLine: (800) 548-6133 (US/Canada Only) • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132

SBOS148

Summary of content (11 pages)

PAGE 1
OPA128 ® Difet ® Electrometer-Grade OPERATIONAL AMPLIFIER FEATURES APPLICATIONS ● ● ● ● ● ● ● ● ● ● ● ULTRA-LOW BIAS CURRENT: 75fA max LOW OFFSET: 500µV max LOW DRIFT: 5µV/°C max HIGH OPEN-LOOP GAIN: 110dB min HIGH COMMON-MODE REJECTION: 90dB min ● IMPROVED REPLACEMENT FOR AD515 AND AD549 ELECTROMETER MASS SPECTROMETER CHROMATOGRAPH ION GAUGE PHOTODETECTOR RADIATION-HARD EQUIPMENT DESCRIPTION The OPA128 is an ultra-low bias current monolithic operational amplifier.
PAGE 2
SPECIFICATIONS ELECTRICAL At VCC = ±15VDC and TA = +25°C, unless otherwise noted. Pin 8 connected to ground.
PAGE 3
ELECTRICAL (FULL TEMPERATURE RANGE SPECIFICATIONS) At VCC = ±15VDC and TA = TMIN and TMAX, unless otherwise noted. OPA128JM PARAMETER CONDITIONS MIN Ambient Temp. 0 TYP OPA128KM MAX MIN +70 0 TYP OPA128LM MAX MIN +70 0 TYP OPA128SM MAX MIN +70 –55 TYP MAX UNITS +125 °C ±170 pA TEMPERATURE RANGE Specification Range INPUT BIAS CURRENT(1) Input Bias Current VCM = 0VDC ±2.5 VCM = 0VDC 1.1 ±8 ±1.3 ±4 ±0.
PAGE 4
DICE INFORMATION PAD FUNCTION 1 2 3 4 5 6 7 8 NC Offset Trim –In +In –VCC Offset Trim Output +VCC Substrate No Connection Substrate Bias: Isolated, normally connected to common. MECHANICAL INFORMATION Die Size Die Thickness Min. Pad Size MILS (0.001") MILLIMETERS 96 x 71 ±5 20 ±3 4x4 2.44 x 1.80 ±0.13 0.51 ±0.08 0.10 x 0.10 Backing OPA128 DIE TOPOGRAPHY None TYPICAL PERFORMANCE CURVES At TA = +25°C, ±15VDC, unless otherwise noted.
PAGE 5
TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°C, +15VDC, unless otherwise noted. BIAS AND OFFSET CURRENT vs TEMPERATURE BIAS AND OFFSET CURRENT vs INPUT COMMON-MODE VOLTAGE 10 Normalized Bias and Offset Current SM 10pA IB 1pA IOS 100 10 1 1 0.1 0.
PAGE 6
TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°C, +15VDC, unless otherwise noted.
PAGE 7
APPLICATIONS INFORMATION The amplifier case should be connected to any input shield or guard via pin 8. This insures that the amplifier itself is fully surrounded by guard potential, minimizing both leakage and noise pickup (see Figure 2). OFFSET VOLTAGE ADJUSTMENT The OPA128 offset voltage is laser-trimmed and will require no further trim for most applications. As with most amplifiers, externally trimming the remaining offset can change drift performance by about 0.
PAGE 8
500Ω 9.5kΩ Guard CF +15V 8 2 7 3 1VDC Output 6 OPA128 1011Ω RF 4 5 2 1 8 Offset Trim 100kΩ pH Probe RS ≈ 500MΩ 50mV Output 10pF 3 ∆Q –15V 6 eO 1011 Ω Low Frequency Cutoff = 1/(2 π RF CF) = 0.16Hz FIGURE 4. Piezoelectric Transducer Charge Amplifier.
PAGE 9
<1pF to prevent gain peaking. 1010Ω Silicon Detector Corp. SD-020-11-21-011 Guard 2 0.01µF 2kΩ 18kΩ 2 Current Input 8 7 OPA128 3 1000MΩ +15V 0.1µF Output 6 3 OPA128 Output 8 5 x 10 9 V/W 0.1µF 6 VO = –1V/nA 4 1010Ω –15V Circuit must be well shielded. FIGURE 7. Sensitive Photodiode Amplifier. FIGURE 8. Current-to-Voltage Converter. +5V 109Ω 2 OPA128 Biased Current Transducer 3 6 8 3 4 5 10 11 12 INA101HP 1 Output 14 +15V 7 5 VO = 1mV/pA 8 REF101 6 +5V 4 1 FIGURE 9.
PAGE 10
PACKAGE OPTION ADDENDUM www.ti.
PAGE 11
IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete.