Data Sheet

ADA4530-1

Femtoampere Input Bias Current Electrometer Amplifier

Rev. C

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FEATURES

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Low input bias current

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±20 fA maximum at TA = 25°C (guaranteed at production test)

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±20 fA maximum at −40°C < TA < +85°C

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±250 fA maximum at −40°C < TA < +125°C (guaranteed at

production test)

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Low offset voltage: 50 µV maximum over specified CMRR range

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Offset voltage drift: ±0.13 µV/°C typical, ±0.5 µV/°C maximum

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Integrated guard buffer with 100 µV maximum offset

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Low voltage noise density: 14 nV/√Hz at 10 kHz

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Wide bandwidth: 2 MHz unity-gain crossover

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Supply voltage: 4.5 V to 16 V (±2.25 V to ±8 V)

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Operating temperature: −40°C to +125°C

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Long-term offset voltage drift (10,000 hours): 0.5 µV typical

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Temperature hysteresis: 1.5 µV typical

APPLICATIONS

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Laboratory and analytical instrumentation: spectrophoto-meters,

chromatographs, mass spectrometers, and potentiostatic and

amperostatic coulometry

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Instrumentation: picoammeters and coulombmeters

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Transimpedance amplifier (TIA) for photodiodes, ion chambers,

and working electrode measurements

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High impedance buffering for chemical sensors and capacitive

sensors

PIN CONNECTION DIAGRAM

Figure 1.

GENERAL DESCRIPTION

The ADA4530-1 is a femtoampere (10−15 A) level input bias current

operational amplifier suitable for use as an electrometer that also

includes an integrated guard buffer. It has an operating voltage

range of 4.5 V to 16 V, enabling it to operate in conventional 5 V

and 10 V single supply systems as well as ±2.5 V and ±5 V dual

supply systems.

It provides ultralow input bias currents that are production tested

at 25°C and at 125°C to ensure the device meets its performance

goals in user systems. The integrated guard buffer isolates the

input pins from leakage in the printed circuit board (PCB), mini-

mizes board component count, and enables easy system design.

The ADA4530-1 is available in an industry-standard surface-mount

8-lead SOIC package with a unique pinout optimized to prevent

signals from coupling between the sensitive input pins, the power

supplies, and the output pin while enabling easy routing of the

guard ring traces.

The ADA4530-1 also offers low offset voltage, low offset drift, and

low voltage and current noise needed for the types of applications

that require such low leakages.

To maximize the dynamic range of the system, the ADA4530-1 has

a rail-to-rail output stage that can typically drive to within 30 mV of

the supply rails under a 10 kΩ load.

The ADA4530-1 operates over the −40°C to +125°C industrial

temperature range and is available in an 8-lead SOIC package.

Figure 2. Input Bias Current (IB) vs. Temperature, VSY = 10 V