Analog Devices AD8628AR, AD8628ART Datasheet

PRELIMINARY TECHNICAL DATA

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Zero-Drift, Single-Supply,

Rail-to-Rail Input/Output

Low Noise Operational Amplifier

Preliminary Technical Data

AD8628

FEATURES

Lowest auto-zero amplifier noise Low Offset Voltage: 5 µV Input Offset Drift: 0.03 µV/°C Rail-to-Rail Input and Output Swing 5 V Single-Supply Operation High Gain, CMRR, and PSRR: 120 dB Very Low Input Bias Current: 100 pA Low Supply Current: 1.3 mA Overload Recovery Time: 0.2 ms No External Components Required

APPLICA TIONS

Automotive Sensors Pressure and Position Sensors Strain Gage Amplifiers Medical Instrumentation Thermocouple Amplifiers

GENERAL DESCRIPTION

This new family of amplifiers has ultra-low offset, drift and bias current. The AD8628 is a wide bandwidth auto-zero amplifier featuring rail-to-rail input and output swings and low noise. Operation is fully specified from 2.7 to 5 volts single supply (±1.35V to ±2.5V dual supply).

The AD8628 family provides the benefits previously found only in expensive auto-zeroing or chopper-stabilized amplifiers. Using Analog Devices’ new topology these zero-drift amplifiers combine low cost, with high accuracy and low noise. (No external capacitors are required.) In addition, the AD8628 greatly reduces the digital switching noise found in most chopper stabilized amplifiers.

With an offset voltage of only 1µV, drift less than 0.005 µV/°C and noise of only 0.5uV P-P (0Hz to 10 Hz) the AD8628 is perfectly suited for applications where error sources cannot be tolerated. Position and pressure sensors, medical equipment, and strain gage amplifiers benefit greatly from nearly zero drift over their opera ting temperature range. Many systems may take advantage of the rail-to-rail input and output swings provided by

the AD8628 family to reduce input biasing complexity and maximi ze SNR.

The AD8628 family is specified for the extended industrial (-40° to +125°C) temperature range. The AD8628 amplifier is available in the tiny SOT23 and the popular 8-pin narrow SOIC plastic packages.

5-Lead SOT

(RT-5)

8-Lead SO

(R-8)

AD8628

PRELIMINARY TECHNICAL DATA

AD8628

– 2 – REV. PrA 1/29/02

ELECTRICAL SPECIFICATIONS

(@ VS=+5.0V, VCM = +2.5V, VO=+2.5V, TA=+25°C unless otherwise specified.)

Parameter Symbol Conditions Min Typ Max Units

INPUT C HARACTERISTICS Offset Voltage VOS 1 5 µV

-40°C ≤ TA ≤ +125°C 10 µV Input Bias Current IB 30 100 pA

-40°C ≤ TA ≤ +125°C 1.5 nA Input Offset Current IOS 50 200 pA

-40°C ≤ TA ≤ +125°C 250 pA Input Voltage Range 0 5 V

Common-Mode Rejection Ratio CMRR VCM = 0V to 5V 120 140 dB

-40°C ≤ TA ≤ +125°C 115 130 dB Large Signal Voltage Gain (No te 1) AVO R

= 10 kΩ, Vo=0.3 to 4.7V 125 145 dB

-40°C ≤ TA ≤ +125°C 120 135 dB Offset Voltage Drift ∆VOS/∆T -40°C ≤ TA ≤ +125°C 0.002 0.03 µV/°C OUTPUT C HARACTERISTICS

Output Voltage High VOH R

= 100kΩ to Ground 4.99 4.996 V

-40°C ≤ TA ≤ +125°C 4.99 4.995 V R

= 10kΩ to Ground 4.95 4.98 V

-40°C ≤ TA ≤ +125°C 4.95 4.97 V Output Voltage Low VOL R

= 100kΩ to V+ 1 10 mV

-40°C ≤ TA ≤ +125°C 2 10 mV R

= 10 kΩ to V+ 10 20 mV

-40°C ≤ TA ≤ +125°C 15 20 mV Short Circuit Limit ISC ± 25 ± 50 mA

-40°C ≤ TA ≤ +125°C ± 40 mA Output Current IO ± 30 mA

-40°C ≤ TA ≤ +125°C ± 15 mA POWER SUPPLY

Power Supply Rejection Ratio PSRR VS = 2.7V to 5.5V 120 130 dB

-40°C ≤ TA ≤ +125°C 115 130 dB Supply Current/Amplifier ISY V

= 0V 1.3 1.5 mA

-40°C ≤ TA ≤ +125°C 1.6 1.8 mA DYNAMIC PERFORMANCE

Slew Rate SR RL =10 kΩ 0.8 V/µs Overload Recovery Time 0.05 0.2 ms

Gain Bandwidth Product GBP 2.5 MHz NOISE PERFORMANCE

Voltage Noise e

n p-p

0.1 to 10 Hz 0.5 µV

p-p

Voltage Noise e

n p-p

0.1 to 1.0 Hz 0.16 µV

p-p

Voltage Noise Density e

f = 1 kHz 22

nV/√Hz

Current Noise Density i

n f=10 Hz 5

fA/√Hz

Note 1: Gain t esting is highly dependent upon test bandwidth.

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