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Fabricante

PA69

Power Operational Amplifier

Apex Microtechnology 

Product Innova tionFrom

PA69

networks are required. The compensation capacitor CC must be rated for a working voltage of the full operating

supply voltage (+VS to –VS). NPO capacitors are recommended to maintain the desired level of compensation over

temperature..

The PA69 requires an external 33pF capacitor between CC- and –Vs to prevent oscillations in the falling edge of the

output. This capacitor should be rated for the full supply voltage (+VS to –VS).

Large Signal Performance

As the amplitude of the input signal increases, the internal dynamic current sources increase the operation band-

width of the amplifier. This unique performance is apparent in its slew rate, pulse response, and large signal perfor-

mance plots. Recall the previous discussion about the relationships between signal amplitude, supply current, and

slew rate. As the amplitude of the input amplitude increases from 1VP-P to 15VP-P, the slew rate increases from 50V/

µs to well over 350V/µs.

The output becomes clipped by the supply rails and the amplifier is no longer operating in a closed loop fashion. The

rise and fall times become faster as the dynamic current sources are providing maximum current for slewing. The

result of this amplifier architecture is that it slews fast, but allows good control of overshoot for large input signals.

This can be seen clearly in the large signal Transient Response plots.

Heatsinking and Safe Operating Area

The MOSFET output stage of the PA69 is not limited by second breakdown considerations as in bipolar output

stages. Only thermal considerations of the package and current handling capabilities limit the Safe Operating Area.

The SOA plots include power dissipation limitations which are dependent upon case temperature. Keep in mind

that the dynamic current sources which drive high slew rates can increase the operating temperature of the ampli-

fier during periods of repeated slewing. The plot of supply current VS. input signal amplitude for a 100 kHz signal

provides an indication of the supply current with repeated slewing conditions. This application dependent condition

must be considered carefully.

The output stage is self-protected against transient flyback by the parasitic body diodes of the output stage. How-

ever, for protection against sustained high energy flyback, external, fast recovery diodes must be used.

Current Limit

For proper operation, the current limit resistor, Rlim, must be connected as shown in the external connections

diagram. For maximum reliability and protection, the largest resistor value should be used. The minimum practical

value for RLIM is about 12Ω. However, refer to the SOA curves for each package type to assist in selecting the opti-

mum value for RLIM in the intended application.

Layout Considerations

The PA69 is built on a dielectrically isolated process and the package tab is therefore not electrically connected

to the amplifier. For high speed operation, the package tab should be connected to a stable reference to reduce

capacitive coupling between amplifier nodes and the floating tab. It is often convenient to directly connect the tab

to GND or one of the supply rails, but an AC connection through a 1uF capacitor to GND is also sufficient if a DC

connection is undesirable

Care should be taken to position the RC / CC compensation networks close to the amplifier compensation pins. Long

loops in these paths pick up noise and increase the likelihood of LC interactions and oscillations.

ELECTROSTATIC DISCHARGE

Like many high performance MOSFET amplifiers, the PA69 very sensitive to damage due to electrostatic discharge

(ESD). Failure to follow proper ESD handling procedures could have results ranging from reduced operating per-

formance to catastrophic damage. Minimum proper handling includes the use of grounded wrist or shoe straps,

grounded work surfaces. Ionizers directed at the work in progress can neutralize the charge build up in the work

environment and are strongly recommended.

PA69U

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