P r o d u c t
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PA85A
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F r o m
PA85,
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PA85 • PA85A
PA85 • PA85A
High Voltage Power Operational Amplifiers
FEATURES
• HIGH VOLTAGE — 450V (±225V)
• HIGH SLEW RATE — 1000V/μS
• HIGH OUTPUT CURRENT — 200mA
APPLICATIONS
• HIGH VOLTAGE INSTRUMENTATION
• PIEZO TRANSDUCER EXCITATION
• PROGRAMMABLE POWER SUPPLIES UP TO 430V
• ELECTROSTATIC TRANSDUCERS & DEFLECTION
PATENTED
8-PIN TO-3
PACKAGE STYLE CE
TYPICAL APPLICATION
Dynamic focusing is the active correction of focusing voltage
as a beam traverses the face of a CRT. This is necessary in
high resolution flat face monitors since the distance between
cathode and screen varies as the beam moves from the center
of the screen to the edges. PA85 lends itself well to this function
since it can be connected as a summing amplifier with inputs
from the nominal focus potential and the dynamic correction.
The nominal might be derived from a potentiometer, or per-
haps automatic focusing circuitry might be used to generate
this potential. The dynamic correction is generated from the
sweep voltages by calculating the distance of the beam from
the center of the display.
DC
FOCUS
X SWEEP
SAMPLE
z=
Y SWEEP
SAMPLE
x
2
+y
2
R
IN2
PA85
TO
FOCUS
GRID
R
IN1
R
F
+225V
R
CL
DESCRIPTION
The PA85 is a high voltage, high power bandwidth MOSFET
operational amplifier designed for output currents up to 200mA.
Output voltages can swing up to ±215V with a dual supply
and up to +440 volts with a single supply. The safe operating
area (SOA) has no second breakdown limitations and can be
observed with all types of loads by choosing an appropriate cur-
rent limiting resistor. High accuracy is achieved with a cascode
input circuit configuration. All internal biasing is referenced to a
bootstrapped zener-MOSFET current source. As a result, the
PA85 features an unprecedented supply range and excellent
supply rejection. The MOSFET output stage is biased on for
linear operation. External compensation provides user flexibility.
This hybrid circuit utilizes thick film (cermet) resistors, ceramic
capacitors and silicon semiconductor chips to maximize reli-
ability, minimize size and give top performance. Ultrasonically
bonded aluminum wires provide reliable interconnections at all
operating temperatures. The 8-pin TO-3 package is hermeti-
cally sealed and electrically isolated. The use of compressible
isolation washers voids the warranty.
EQUIVALENT SCHEMATIC
3
+V
S
Q9
C
L
Q12
2
-225V
EXTERNAL CONNECTIONS
+Vs
CL
D1
Q1
Q2
Q4
D23
COMP
7
8
–IN
5
Q6
Q10A
Q7
Q10B
+IN
4
3
2
R
CL
Q8
+IN
4
TOP VIEW
–IN
1
OUT
Q11
1
OUT
Q17
Q18
Q16
5
6
7
COMP
8
–Vs
COMP
C
C
Q13
D2
R
C
–V
S
6
PHASE COMPENSATION
R
C
Gain
C
C
1
68pF
100Ω
20
10pF
330Ω
100
3.3pF
0Ω
C
C
RATED FOR FULL
SUPPLY VOLTAGE
PA85U
http://www.cirrus.com
Copyright © Cirrus Logic, Inc. 2009
(All Rights Reserved)
MAY 2009
1
APEX − PA85UREVO
CIRRUS [ CIRRUS LOGIC ]
