PA92 データシートの表示（PDF） - Cirrus Logic

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PA92

High Voltage Power Operational Amplifiers

Cirrus Logic 

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PA92

SAFE OPERATING CURVES

The safe operating area curves define the maximum additional internal power dissipation the amplifier can tolerate

when it produces the necessary output to drive an external load.

INPUT PROTECTION

Although the PA92 can withstand differential voltages up to ±20V, ad-

ditional external protection is recommended. Low leakage, low capaci-

tance JFETs connected as diodes are recommended (e.g. 2N4416, Q1-

Q4 in Figure 2). The differential input voltage will be clamped to ±1.4V.

This is sufficient overdrive to produce maximum power bandwidth.

–IN

Q1

+VS

Z1

1

11, 12

Q3

6

PA90

POWER SUPPLY PROTECTION

Q2

+IN

Unidirectional zener diode transient suppressors are recommended as

Q4

2

7, 8

protection on the supply pins. See Figure 2. The zeners clamp transients

to voltages within the power supply rating and also clamp power supply

reversals to ground. Whether the zeners are used or not, the system

FIGURE 2.

OVERVOLTAGE

PROTECTION

Z2

–VS

power supply should be evaluated for transient performance including

power-on overshoot and power-off polarity reversals as well as line regulation.

Conditions which can cause open circuits or polarity reversals on either power supply rail should be avoided or pro-

tected against. Reversals or opens on the negative supply rail is known to induce input stage failure. Unidirectional

transzorbs prevent this, and it is desirable that they be both electrically and physically as close to the amplifier as

possible.

STABILITY

The PA92 is externally compensated and performance can be tailored to the application. Use the graphs of small

signal response and power response as a guide. The compensation capacitor CC must be rated at 500V working

voltage. An NPO capacitor is recommended. The compensation network CCRC must be mounted closely to the am-

plifier pins 4 and 5 to avoid spurious oscillation.

QUIESCENT CURRENT REDUCTION

When pin 3 (IQ) is shorted to pin 5 (CC2) the AB biasing of the output stage is disabled. This lowers quiescent power

but also raises distortion since the output stage is then class C biased. The output stage bias current is nominally

set at 1mA. Pin 3 may be left open if not used.

PA92U

5

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