16 V Auto-Zero, Rail-to-Rail Output

Operational Amplifiers

AD8638/AD8639

Rev. F

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FEATURES

Low offset voltage: 9 μV maximum

Offset drift: 0.04 μV/°C maximum

Rail-to-rail output swing

5 V to 16 V single-supply or ±2.5 V to ±8 V dual-supply

operation

High gain: 136 dB typical

High CMRR: 133 dB typical

High PSRR: 143 dB typical

Very low input bias current: 40 pA maximum

Low supply current: 1.3 mA maximum

AD8639: qualified for automotive applications

APPLICATIONS

Pressure and position sensors

Strain gage amplifiers

Medical instrumentation

Thermocouple amplifiers

Automotive sensors

Precision references

Precision current sensing

GENERAL DESCRIPTION

The AD8638/AD8639 are single and dual wide bandwidth,

auto-zero amplifiers featuring rail-to-rail output swing and low

noise. These amplifiers have very low offset, drift, and bias

current. Operation is fully specified from 5 V to 16 V single

supply (±2.5 V to ±8 V dual supply).

The AD8638/AD8639 provide benefits previously found only

in expensive zero-drift or chopper-stabilized amplifiers. Using

the Analog Devices, Inc., topology, these auto-zero amplifiers

combine low cost with high accuracy and low noise. No exter-

nal capacitors are required. In addition, the AD8638/AD8639

greatly reduce the digital switching noise found in most chopper-

stabilized amplifiers.

With a typical offset voltage of only 3 μV, drift of 0.01 μV/°C,

and noise of 1.2 μV p-p (0.1 Hz to 10 Hz), the AD8638/AD8639

are 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 ranges. Many systems can take

advantage of the rail-to-rail output swing provided by the

AD8638/AD8639 to maximize signal-to-noise ratio (SNR).

PIN CONFIGURATIONS

OUT

1

V–

2

+IN

3

V+

5

–IN

4

AD8638

TOP VIEW

(Not to Scale)

Figure 1. 5-Lead SOT-23 (RJ-5)

NC

1

–IN

2

+IN

3

V–

4

NC

8

V+

7

OUT

6

NC

5

NC = NO CONNECT

AD8638

TOP VIEW

(Not to Scale)

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

–IN A

2

+IN A

3

V–

4

V+

8

OUT B

7

–IN B

6

+IN B

5

AD8639

TOP VIEW

(Not to Scale)

Figure 3. 8-Lead MSOP (RM-8)

8-Lead SOIC_N (R-8)

PIN 1

INDICATOR

NOTES

1. PIN 4 AND THE EXPOSED PAD

MUST BE CONNECTED TO V–.

AD8639

1

OUT A

2

–IN A

3

+IN A

4

v–

7OUT B

8V+

6 –IN B

5 +IN B

TOP VIEW

(Not to Scale)

Figure 4. 8-Lead LFCSP_WD (CP-8-5)

The AD8638/AD8639 are specified for the extended industrial

temperature range (−40°C to +125°C). The single AD8638 is

available in tiny 5-lead SOT-23 and 8-lead SOIC packages.

The dual AD8639 is available in 8-lead MSOP, 8-lead SOIC, and

8-lead LFCSP packages. See the Ordering Guide for automotive

grades.

The AD8638/AD8639 are members of a growing series of auto-

zero op amps offered by Analog Devices (see Table 1).

Table 1. Auto-Zero Op Amps

Supply

2.7 V to 5 V

2.7 V to 5 V Low Power

5 V to 16 V

Single

AD8628

AD8538

AD8638

Dual

AD8629

AD8539

AD8639

Quad

AD8630