APEX MICROTECHNOLOGY CORPORATION • 5980 NORTH SHANNON ROAD • TUCSON, ARIZONA 85741 • USA • APPLICATIONS HOTLINE: 1 (800) 546–2739

4

PA86

OPERATING

CONSIDERATIONS

EXTERNAL CONNECTIONS

SMALL SIGNAL GAIN AND PHASE PLOTS

The input signal amplitude to the PA86 ampli-

fier is related to the overall phase margin and

unity gain bandwidth. For very small signal am-

plitudes the amplifier phase margin is negative

and it shows instability. If small signal stability

is desired a constant current source of 500 uA

(or resistor for constant supply voltage) needs

to be added externally between C

This current source has minor effects on output

offset voltage but helps immensely with small

signal stability. The following gain and phase

plots have been generated with a 100k resistor

(fixed dual supply voltage +/– 50V) between

C

bandwidth and phase margin improves with

larger signal amplitude because of the unique

differential amplifier stage in the PA86.

SAFE OPERATING AREA

The MOSFET output stage of the PA86 is not limited by

second breakdown considerations as in bipolar output stages.

Only thermal considerations and current handling capabilities

limit the SOA. The output stage is protected against transient

flyback by the parasitic body diodes of the output stage MOS-

FET structure. However, for protection against sustained high

energy flyback external fast–recovery diodes must be used.