PA61U

1

PA61 • PA61A

P r o d u c t I n n o v a t i o n F r o m

Copyright © Cirrus Logic, Inc. 2007

(All Rights Reserved)

Cirrus Logic, Inc.

http://www.cirrus.com

NOV 2007

PA61U rev K

FEATURES

•WIDESUPPLYRANGE—±10to±45V

•HIGHOUTPUTCURRENT—±10APeak

•LOWCOST—Class“C”outputstage

•LOWQUIESCENTCURRENT—3mA

APPLICATIONS

•PROGRAMMABLEPOWERSUPPLY

•MOTOR/SYNCRODRIVER

•VALVEANDACTUATORCONTROL

•DCORACPOWERREGULATOR

•FIXEDFREQUENCYPOWEROSCILLATOR

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”.

EQUIVALENTSCHEMATIC

TYPICALAPPLICATION

Due to its high current drive capability, PA61 applications

often utilize remote sensing to compensate IR drops in the wir-

ing. The importance of remote sensing increases as accuracy

requirements, output currents, and distance between ampli-

fier 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

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.

EXTERNALCONNECTIONS

PA61 • PA61A

P r o d u c t I n n o v a t i o n F r o m

8-PINTO-3

PACKAGESTYLECE