The PA85 is a high voltage, high power bandwidth MOS-FET operational amplifier designed for output currents up to 200mA. Output voltages can swing up to ±215V with a dual supply and up to +440 volts with a single supply. The safe operating area (SOA) has no second breakdown limitations and can be observed with all types of loads by choosing an appropriate current limiting resistor. High accuracy is achieved with a cascode input circuit configuration. All internal biasing is referenced to a bootstrapped zener-MOSFET current source. As a result, the PA85 features an unprecedented supply range and excellent supply rejection. The MOSFET output stage is biased on for linear operation. External compensation provides user flexibility. This hybrid circuit utilizes thick film (cermet) resistors, ceramic capacitors and silicon semiconductor chips to maximize reli- ability, minimize size and give top performance. Ultrasonically bonded aluminum wires provide reliable interconnections at all operating temperatures. The 8-pin TO-3 package is hermeti- cally sealed and electrically isolated.
The PA85/PA85A series are high‑voltage, high‑power bandwidth MOS‑FET operational amplifiers designed for applications such as high‑voltage instrumentation, piezo transducer excitation, programmable power supplies, and electrostatic deflection. They feature a 450 V supply range, 200 mA continuous output current, and a high slew rate of up to 1000 V/µs.
The datasheet provides absolute maximum ratings, detailed electrical specifications, and operating considerations including current‑limit resistor selection, safe operating area (SOA) curves, input and power‑supply protection, and stability compensation guidelines.
| Supply Voltage (max) | 450 V |
|---|---|
| Continuous Output Current | 200 mA |
| Power Dissipation (continuous) | 30 W |
| Input Offset Voltage (typical) | 5 mV |
| Gain‑Bandwidth Product | 100 MHz |
| Slew Rate (max) | 1000 V/µs |
| Operating Temperature Range (case) | -25 °C to +85 °C |
The maximum supply voltage is 450 V.
It can deliver up to 200 mA continuous output current.
The typical gain‑bandwidth product is 100 MHz.
The minimum value is 1.4 Ω, but a higher value up to 30 Ω is recommended for reliability.