PRODUCT DESCRIPTION

The AD549 is a monolithic electrometer operational amplifier with very low input bias current. Input offset voltage and input offset voltage drift are laser trimmed for precision performance. The AD549’s ultralow input current is achieved with “Topgate” JFET technology, a process development exclusive to Analog Devices. This technology allows the fabrication of extremely low input current JFETs compatible with a standard junction isolated bipolar process. The 1015 Ω common-mode impedance, a result of the bootstrapped input stage, insures that the input current is essentially independent of common-mode voltage.

FEATURES

Ultralow Bias Current: 60 fA max (AD549L) 250 fA max (AD549J)

Input Bias Current Guaranteed Over Common-Mode Voltage Range

Low Offset Voltage: 0.25 mV max (AD549K) 1.00 mV max (AD549J)

Low Offset Drift: 5 μV/8C max (AD549K) 20 μV/8C max (AD549J)

Low Power: 700 μA max Supply Current

Low Input Voltage Noise: 4 μV p-p 0.1 Hz to 10 Hz

MIL-STD-883B Parts Available

APPLICATIONS

Electrometer Amplifiers

Photodiode Preamp

pH Electrode Buffer

Vacuum lon Gage Measurement