DESCRIPTION
The PA85 is a high voltage, high power bandwidth MOSFET 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.

FEATURES
• HIGH VOLTAGE — 450V (±225V)
• HIGH SLEW RATE — 1000V/μS
• HIGH OUTPUT CURRENT — 200mA

APPLICATIONS
• HIGH VOLTAGE INSTRUMENTATION
• PIEZO TRANSDUCER EXCITATION
• PROGRAMMABLE POWER SUPPLIES UP TO 430V
• ELECTROSTATIC TRANSDUCERS & DEFLECTION

TYPICAL APPLICATION
Dynamic focusing is the active correction of focusing voltage as a beam traverses the face of a CRT. This is necessary in high resolution flat face monitors since the distance between cathode and screen varies as the beam moves from the center of the screen to the edges. PA85 lends itself well to this function since it can be connected as a summing amplifier with inputs from the nominal focus potential and the dynamic correction. The nominal might be derived from a potentiometer, or perhaps automatic focusing circuitry might be used to generate this potential. The dynamic correction is generated from the sweep voltages by calculating the distance of the beam from the center of the display.