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5

PA09 • PA09A

affect both supply rating and thermal ratings. When calculat-

ing internal power dissipation, multiply this current times total

supply voltage.

Note that swinging closer to the supply rail demands more

current. Output voltage is given as peak. Currents are aver-

age responding supply readings, but AC monitoring will reveal

current pulses corresponding to periods of high slew rate.

For example, driving ±30V outputs at 500KHz on ±40V sup-

plies produces a .8A pulse during negative slew and a 1.2A

pulse during positive slew. If the input signal is over driven

by several times the output swing capability, pulses up to 4A

may be seen.

THERMAL SHUTDOWN PROTECTION

The thermal protection circuit shuts off the amplifier when

the substrate temperature exceeds approximately 150°C. This

allows heatsink selection to be based on normal operating

conditions while protecting the amplifier against excessive

junction temperature during temporary fault conditions.

Thermal protection is a fairly slow-acting circuit and therefore

does not protect the amplifier against transient SOA violations

(areas outside of the T

protect against short-term fault conditions that result in high

power dissipation within the amplifier, If the conditions that

cause thermal shutdown are not removed, the amplifier will

OPERATING

CONSIDERATIONS

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oscillate in and out of shutdown. This will result in high peak

power stresses, destroy signal integrity, and reduce the reli-

ability of the device.

STABILITY

Due to its large bandwidth the PA09 is more likely to os-

cillate than lower bandwidth Power Operational Amplifiers.

To prevent oscillations a reasonable phase margin must be

maintained by:

1. Pay very careful attention to supply bypassing and circuit

grounding. This is very important when step functions are

driven and the PA09 shares supplies with more active

devices.

2. Keeping the external sumpoint stray capacitance to ground

at a minimum and the sumpoint load resistance (input and

feedback resistors in parallel) below 500Ω. Larger sumpoint

load resistances can be used with increased phase com-

pensation and/or bypassing of the feedback resistor.

3. Connect the case to a local AC ground potential.

CURRENT LIMIT

Internal current limiting is provided in the PA09. Note the

current limit curve given under typical performance graphs is

based on junction temperature. If the amplifier is operated at

cold junction temperatures, current limit could be as high as 8

amps. This is above the maximum allowed current on the SOA

curve of 5 amps. Systems using this part must be designed to

keep the maximum output current to less than 5 amps under all

conditions. The internal current limit only provides this protec-

tion for junction temperatures of 80°C and above.

This data sheet has been carefully checked and is believed to be reliable, however, no responsibility is assumed for possible inaccuracies or omissions. All specifications are subject to change without notice.

PA09U REV K AUGUST 2005 © 2005 Apex Microtechnology Corp.