APEX MICROTECHNOLOGY CORPORATION
TELEPHONE (520) 690-8600 FAX (520) 888-3329 ORDERS (520) 690-8601 EMAIL prodlit@apexmicrotech.com
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
DESCRIPTION
The PA61 and PA61A are high output current operational
amplifiers designed to drive resistive, inductive and capacitive
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 reliability,
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 Consid-
erations”.
EQUIVALENT SCHEMATIC
TOP VIEW
1
2
3
4
5
6
7
8
C
L
–
–
V
S
+IN
–
IN
+V
S
OUT
N.C.
C
L+
R
CL+
R
CL
–
OUTPUT
+42V
–
42V
R
F1
PA61
R
CL+
R
CL
–
R
F2
R
W
RTN
SENSE LO
R
W
±10V
DAC
SENSE HI
LOAD
R
IN1
R
IN2
OUT
FIGURE 1. PROGRAMMABLE POWER SUPPLY
WITH REMOTE SENSING
2
8
1
3
6
4
5
A1
Q3
Q4
C1
Q1A
Q1B
Q6B
Q6A
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 accu-
racy requirements, output currents, and distance between
amplifier and load go up. The circuit above shows wire
resistance 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
/R
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.
EXTERNAL CONNECTIONS
HTTP://WWW.APEXMICROTECH.COM (800) 546-APEX (800) 546-2739
M I C R O T E C H N O L O G Y
POWER OPERATIONAL AMPLIFIERS
PA61 PA61A