a 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 V/؇C max (AD549K) 20 V/؇C max (AD549J) Low Power: 700 A max Supply Current Low Input Voltage Noise: 4 V p 0.1 Hz to 10 Hz MIL-STD-883B Parts Available APPLICATIONS Electrometer Amplifiers Photodiode Preamp pH Electrode Buffer Vacuum lon Gage Measurement
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 junctionisolated 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. The AD549 is suited for applications requiring very low input current and low input offset voltage. It excels as a preamp for a wide variety of current output transducers such as photodiodes, photomultiplier tubes, or oxygen sensors. The AD549 can also be used as a precision integrator or low droop sample and hold. The AD549 is pin compatible with standard FET and electrometer op amps, allowing designers to upgrade the performance of present systems at little additional cost. The AD549 is available in a TO-99 hermetic package. The case is connected to Pin 8 so that the metal case can be independently connected to a point at the same potential as the input terminals, minimizing stray leakage to the case. *Protected by Patent No. 4,639,683.
Ultralow Input Bias Current Operational Amplifier AD549* CONNECTION DIAGRAM GUARD PIN, CONNECTED TO CASE NC OFFSET NULL
INVERTING 2 INPUT
6 OUTPUT 3
V– 10kΩ 5
VOS TRIM NC = NO CONNECTION
The AD549 is available in four performance grades. The J, K, and L versions are rated over the commercial temperature range 0°C to +70°C. The S grade is specified over the military temperature range of –55°C to +125°C and is available processed to MIL-STD-883B, Rev C. Extended reliability PLUS screening is also available. Plus screening includes 168-hour burn-in, as well as other environmental and physical tests derived from MIL-STD-883B, Rev C. PRODUCT HIGHLIGHTS
1. The AD549’s input currents are specified, 100% tested and guaranteed after the device is warmed up. Input current is guaranteed over the entire common-mode input voltage range. 2. The AD549’s input offset voltage and drift are laser trimmed to 0.25 mV and 5 µV/°C (AD549K), 1 mV and 20 µV/°C (AD549J). 3. A maximum quiescent supply current of 700 µA minimizes heating effects on input current and offset voltage. 4. AC specifications include 1 MHz unity gain bandwidth and 3 V/µs slew rate. Settling time for a 10 V input step is 5 µs to 0.01%. 5. The AD549 is an improved replacement for the AD515, OPA104, and 3528.
REV. A Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 617/329-4700 Fax: 617/326-8703