The AD549 is a monolithic electrometer operational amplifier with ultralow input bias current, low input voltage noise, and low power consumption. It is primarily used for electrometer amplifier, photodiode preamp, pH electrode buffer, vacuum ion gauge measurement and other applications.
The AD549 is a monolithic electrometer operational amplifier offering ultralow input bias current (as low as 60 fA) and low offset voltage. It uses Analog Devices' exclusive Topgate™ JFET technology and provides a 10^15 Ω common‑mode impedance, making it suitable for precision electrometer, photodiode, and pH‑probe applications.
The device is supplied in a TO‑99 hermetic metal can and is available in four performance grades (J, K, L, S) covering commercial and military temperature ranges. Detailed specifications, typical performance curves, and design guidelines are included to aid circuit designers in minimizing leakage currents and optimizing accuracy.
| Input bias current (AD549L) | 60 fA max |
|---|---|
| Input offset voltage (AD549K) | 0.25 mV max |
| Unity‑gain bandwidth | 1 MHz |
| Supply voltage rating | ±18 V |
The AD549L version has a maximum input bias current of 60 fA.
The device is rated for a supply voltage of up to ±18 V.
The AD549 provides a unity‑gain bandwidth of 1 MHz.