鈥?HIGH OUTPUT CURRENT 鈥?/div>
鹵10A
Peak
鈥?LOW COST 鈥?Class 鈥淐鈥?output stage
鈥?LOW QUIESCENT CURRENT 鈥?3mA
APPLICATIONS
鈥?PROGRAMMABLE POWER SUPPLY
鈥?MOTOR/SYNCRO DRIVER
鈥?VALVE AND ACTUATOR CONTROL
鈥?DC OR AC POWER REGULATOR
鈥?FIXED FREQUENCY POWER OSCILLATOR
R
F1
SENSE HI
+42V
R
CL+
鹵10V R
IN1
DAC
OUT
R
W
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 鈥淕eneral Operating Consid-
erations鈥?
R
IN2
PA61
R
CL鈥?/div>
鈥?2V
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 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
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+
Q3
4
A1
5
1
+V
S
3
C
L+
2
1
OUT
Q4
+IN
OUTPUT
4
C1
Q6A
6
8
5
TOP VIEW
鈥揑N
6
Q6B
R
CL鈥?/div>
8
7
鈥揤
S
C
L鈥?/div>
N.C.
APEX MICROTECHNOLOGY CORPORATION
鈥?TELEPHONE (520) 690-8600 鈥?FAX (520) 888-3329 鈥?ORDERS (520) 690-8601 鈥?EMAIL prodlit@apexmicrotech.com
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