Zero-Drift, Single-Supply, Rail-to-Rail

Input/Output Operational Amplifier

AD8628/AD8629

Rev. C

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FEATURES

Lowest auto-zero amplifier noise

Low offset voltage: 1 µV

Input offset drift: 0.002 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 max

Low supply current: 1.0 mA

Overload recovery time: 10 µs

No external components required

APPLICATIONS

Automotive sensors

Pressure and position sensors

Strain gage amplifiers

Medical instrumentation

Thermocouple amplifiers

Precision current sensing

Photodiode amplifier

PIN CONFIGURATIONS

OUT

1

V–

2

+IN

3

V+

5

–IN

4

AD8628

TOP VIEW

(Not to Scale)

Figure 1. 5-Lead TSOT (UJ-5)

and 5-Lead SOT-23 (RT-5)

NC

1

–IN

2

+IN

3

V–

4

NC

8

V+

7

OUT

6

NC

5

NC = NO CONNECT

AD8628

TOP VIEW

(Not to Scale)

Figure 2. 8-Lead SOIC (R-8)

OUT A

1

–IN A

2

+IN A

3

V–

4

V+

8

OUT B

7

–IN B

6

+IN B

5

AD8629

TOP VIEW

(Not to Scale)

Figure 3. 8-Lead SOIC (R-8)

OUT A

1

–IN A

2

+IN A

3

V–

4

V+

8

OUT B

7

–IN B

6

+IN B

5

AD8629

TOP VIEW

(Not to Scale)

Figure 4. 8-Lead MSOP (RM-8)

GENERAL DESCRIPTION

This new breed of amplifier has ultralow offset, drift, and bias

current. The AD8628/AD8629 are wide bandwidth auto-zero

amplifiers featuring rail-to-rail input and output swings and low

noise. Operation is fully specified from 2.7 V to 5 V single

supply (±1.35 V to ±2.5 V dual supply).

The AD8628/AD8629 provide 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 exter-

nal capacitor is required.) In addition, the AD8628/AD8629

greatly reduce the digital switching noise found in most

chopper-stabilized amplifiers.

With an offset voltage of only 1 µV, drift of less than

0.005 µV/°C, and noise of only 0.5 µV p-p (0 Hz to 10 Hz),

the AD8628/AD8629 are perfectly suited for applications in

which error sources cannot be tolerated. Position and pressure

sensors, medical equipment, and strain gage amplifiers benefit

greatly from nearly zero drift over their operating temperature

range. Many systems can take advantage of the rail-to-rail input

and output swings provided by the AD8628/AD8629 to reduce

input biasing complexity and maximize SNR.

The AD8628/AD8629 are specified for the extended industrial

temperature range (−40°C to +125°C). The AD8628 is available

in tiny TSOT-23, SOT-23, and the popular 8-lead narrow SOIC

plastic packages. The AD8629 is available in the standard 8-lead

narrow SOIC and MSOP plastic packages.