PA40 Datasheet, PDF (4/4 Pages) List of Unclassifed Manufacturers – HIGH VOLTAGE POWER OPERATIONAL AMPLIFIER

PA40
OPERATING
CONSIDERATIONS
GENERAL
Please read Application Note 1 "General Operating
Considerations" which covers stability, supplies, heat sinking,
mounting, current limit, SOA interpretation, and specification
interpretation. Visit www.apexmicrotech.com for design tools
that help automate tasks such as calculations for stability,
internal power dissipation, current limit; heat sink selection;
Apex’s complete Application Notes library; Technical Seminar
Workbook; and Evaluation Kits.
INPUT PROTECTION
The PA40 inputs are protected against common mode
voltages up the supply rails and differential voltages up to
±16 volts as well as static discharge. Differential voltages
exceeding 16 volts will be clipped by the protection circuitry.
However, if more than a few milliamps of current is available
from the overload source, the protection circuitry could be
destroyed. The protection circuitry includes 300 ohm current
limiting resistors at each input, but this may be insufficient
for severe overloads. It may be necessary to add external
resistors to the application circuit where severe overload
conditions are expected. Limiting input current to 1mA will
prevent damage.
STABILITY
The PA40 has sufficient phase margin when compensated
for unity gain to be stable with capacitive loads of at least
10 nF. However, the low pass circuit created by the sumpoint
(–in) capacitance and the feedback network may add phase
shift and cause instabilities. As a general rule, the sumpoint
load resistance (input and feedback resistors in parallel)
should be 1K ohm or less at low gain settings (up to 10).
Alternatively, use a bypass capacitor across the feedback
resistor. The time constant of the feedback resistor and bypass
capacitor combination should match the time constant of the
sumpoint resistance and sumpoint capacitance.
The PA40 is externally compensated and performance can
be tailored to the application. Use the graphs of small signal
gain and phase response as well as the graphs for slew rate
and power response as a guide. The compensation capacitor
C_C must be rated at 250V working voltage. The compensation
capacitor and associated resistor R_C must be mounted closely
to the amplifier pins to avoid spurious oscillation. An NPO
capacitor is recommended for compensation.
SAFE OPERATING AREA (SOA)
The MOSFET output stage of this power operational
amplifier has two distinct limitations:
1. The current handling capability of the die metallization.
2. The temperature of the output MOSFETs.
NOTE: The output stage is protected against transient
flyback. However, for protection against sustained, high energy
flyback, external fast-recovery diodes should be used.
200
120
100
50
40
30
20
10
5
4
3
2
10
PA40 SOA
200mS
300mS
DC,
T
C
=
DC, _TC
85_°C
= _25°C
20 30 50
100 200 300 500
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PA40U REV. B JUNE 2001 © 2001 Apex Microtechnology Corp.