P r o d u c t I
n n o v a
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nnova
PA61,
I
PA61A
o n
F
F
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PA61 • PA61A
PA61 • PA61A
Power Operational Amplifiers
FEATURES
• WIDE SUPPLY RANGE — ±10 to ±45V
• HIGH OUTPUT CURRENT — ±10A Peak
• LOW COST — Class “C” output stage
• LOW QUIESCENT CURRENT — 3mA
APPLICATIONS
• PROGRAMMABLE POWER SUPPLY
• MOTOR/SYNCRO DRIVER
• VALVE AND ACTUATOR CONTROL
• DC OR AC POWER REGULATOR
• FIXED FREQUENCY POWER OSCILLATOR
8-PIN TO-3
PACKAGE STYLE CE
R
F1
SENSE HI
+42V
±10V R
IN1
DAC
R
CL+
OUT
R
W
DESCRIPTION
The PA61 and PA61A are high output current operational
amplifiers designed to drive resistive, inductive and capaci-
tive loads. Their complementary emitter follower output stage
is the simple class C type and optimized for low frequency
applications where crossover distortion is not critical. These
amplifiers are not recommended for audio, transducer or
deflection coil drive circuits above 1kHz or when distortion is
critical. The safe operating area (SOA) is fully specified and
can be observed for all operating conditions by selection of
user programmable current limiting resistors. Both amplifiers
are internally compensated for all gain settings. For continu-
ous operation under load, mounting on a heatsink of proper
rating is recommended.
This hybrid circuit utilizes thick film conductors, ceramic
capacitors, and semiconductor chips to maximize reliabil-
ity, minimize size, and give top performance. Ultrasonically
bonded aluminum wires provide reliable interconnections at
all operating temperatures. The 8-pin TO-3 package is electri-
cally isolated and hermetically sealed. The use of compres-
sible thermal washers and/or improper mounting torque
voids the product warranty. Please see “General Operating
Considerations”
.
R
IN2
PA61
R
CL–
–42V
LOAD
R
F2
SENSE LO
RTN
R
W
FIGURE 1. PROGRAMMABLE POWER SUPPLY
WITH REMOTE SENSING
TYPICAL APPLICATION
Due to its high current drive capability, PA61 applications
often utilize remote sensing to compensate IR drops in the
wiring. The importance of remote sensing increases as ac-
curacy requirements, output currents, and distance between
amplifier and load go up. The circuit above shows wire resis-
tance from the PA61 to the load and back to the local ground
via the power return line. Without remote sensing, a 7.5A load
current across only 0.05 ohm in each line would produce a
0.75V error at the load.
With the addition of the second ratio matched R
F
/R
IN
pair
and two low current sense wires, IR drops in the power return
line become common mode voltages for which the op amp
has a very high rejection ratio. Voltage drops in the output and
power return wires are inside the feedback loop. Therefore, as
long as the Power Op Amp has the voltage drive capability to
overcome the IR losses, accuracy remains the same. Applica-
tion Note 7 presents a general discussion of PPS circuits.
EQUIVALENT SCHEMATIC
3
Q1A
Q1B
2
EXTERNAL CONNECTIONS
R
CL+
C
L+
3
4
Q3
A1
1
+V
S
+IN
4
2
1
5
OUT
Q4
C1
Q6A
6
8
OUTPUT
TOP VIEW
5
Q6B
–IN
6
8
7
R
CL–
C
L–
–V
S
N.C.
PA61U
http://www.cirrus.com
Copyright © Cirrus Logic, Inc. 2009
(All Rights Reserved)
MAY 2009
1
APEX − PA61UREVL
CIRRUS [ CIRRUS LOGIC ]
