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

4

PA79

OPERATING

CONSIDERATIONS

EXTERNAL CONNECTIONS

SMALL SIGNAL GAIN AND PHASE PLOTS

The input signal amplitude to the PA79

amplifier is related to the overall phase

margin and unity gain bandwidth. For very

small signal amplitudes the amplifier phase

margin is negative and it shows instability.

If small signal stability is desired a con-

stant 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

note that the unity gain bandwidth and

phase margin improves with larger signal

amplitude because of the unique differential

amplifier stage in the PA79.

SAFE OPERATING AREA

The MOSFET output stage of the PA79

is not limited by second breakdown con-

siderations 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 MOSFET structure. However,

for protection against sustained high energy

flyback external fast–recovery diodes must

be used.

NOTES:

1. The package heat slug needs to be connected to a stable refer-

ence such as gnd for high slew rates. Please refer to special

considerations section for details.

2. Supply bypassing required for –Vs and +Vs.

3. For Cc and Rc values refer to power supply biasing section.

4. Dimple and ESD triangle denotes pin 1.