PA42A Apex Microtechnology, PA42A Datasheet - Page 4

• Manufacturer Part Number: PA42A
• Description: (PA41 / PA42) HIGH VOLTAGE POWER OPERATIONAL AMPLIFIERS
• Manufacturer: Apex Microtechnology

PA41/PA42 • PA41A/PA42A
GENERAL
erations" which covers stability, supplies, heat sinking, mount-
ing, current limit, SOA interpretation, and specification inter-
pretation. 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 Work-
book; and Evaluation Kits.
CURRENT LIMIT
connected as shown in the external connection diagram. The
minimum value is 18 ohms, however for optimum reliability the
resistor value should be set as high as possible. The value can
be estimated as follows with the maximum practical value of
500 ohms.
variations in current limit value with a given R
over temperature. The selected value of R
the specified typical value of output resistance to calculate the
total output resistance. Since the load current passes through
R
according to:
signal spurious oscillation present during the current limited
portion of the negative half cycle. The frequency of the oscil-
lation is not predictable and depends on the compensation,
gain of the amplifier, and load. The oscillation will cease as the
amplifier comes out of current limit.
INPUT PROTECTION
voltages up the supply rails and differential voltages up to 16
volts as well as static discharge. Differential voltages exceed-
ing 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 ex-
pected. Limiting input current to 1mA will prevent damage.
STABILITY
sated 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 5K 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.
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.
CL
Please read Application Note 1 "General Operating Consid-
For proper operation the current limit resistor, R
Use the typical performance graphs as a guide for expected
When the amplifier is current limiting, there may be small
The PA41/42 inputs are protected against common mode
The PA41/42 has sufficient phase margin when compen-
the value selected also affects the output voltage swing
where V
R
is the voltage swing reduction.
R
CL
V
=
R
= I
I
LIM
3
O
*
R
CL
PA41/42U REV. G JANUARY 1999 © 1999 Apex Microtechnology Corp.
CL
must be added to
CL
and variations
CL
, must be
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
compensation capacitor and associated resistor R
mounted closely to the amplifier pins to avoid spurious oscilla-
tion. An NPO capacitor is recommended for compensation.
SAFE OPERATING AREA (SOA)
fier has two distinct limitations:
1. The current handling capability of the die metallization.
2. The temperature of the output MOSFETs.
flyback. However, for protection against sustained, high en-
ergy flyback, external fast-recovery diodes should be used.
The PA41/42 is externally compensated and performance
The MOSFET output stage of this power operational ampli-
NOTE: The output stage is protected against transient
200
120
100
200
120
100
50
40
30
20
10
50
40
30
20
10
5
4
3
2
5
4
3
2
10
10
C
PULSE CURVES @ 10% DUTY CYCLE MAX
PULSE CURVES @ 10% DUTY CYCLE MAX
SUPPLY TO OUTPUT DIFFERENTIAL, V
SUPPLY TO OUTPUT DIFFERENTIAL, V
must be rated at 350V working voltage. The
20
20
30
30
50
50
PA41 SOA
PA42 SOA
100
100
300mS
CONSIDERATIONS
200 300
200 300
S
S
-V
-V
200mS
O
O
OPERATING
(V)
(V)
C
500
500
must be