PA50 • PA50A
GENERAL
Please read Application Note 1 "General Operating Con-
siderations" which covers stability, supplies, heat sinking,
mounting, current limit, SOA interpretation, and specification
interpretation. Visit www.apexmicrotech.com for design tools
that help automate tasks such as calculations for stability,
internal power dissipation, current limit; heat sink selection;
Apex’s complete Application Notes library; Technical Seminar
Workbook; and Evaluation Kits.
OPERATING
CONSIDERATIONS
COMPENSATION
Compensation is internally fixed for a gain of 3 or more and
is not adjustable by the user. The PA50 therefore is not unity
gain stable.
POWER SUPPLY BYPASSING
Proper and sufficient power supply bypassing is crucial to
proper operation of the PA50. Bypass the +Vb and -Vb supply
pins with a minimum .1µF ceramic capacitors directly at the
supply pins. On the +Vs and -Vs pins use a combination of
ceramic and electrolytic capacitors. Use 1µF ceramic capaci-
tors and an electrolytic capacitor at least 10µF for each amp
of output current required.
CURRENT LIMIT
There is no internal circuit provision for current limit in the
PA50. However, the PA50 circuit board in the PA50 evaluation
kit does provide a means whereby the output current can be
sensed. An external circuit current limit can thereby be imple-
mented if needed. See EK27 data sheet for more details.
BOOST OPERATION
With the V
BOOST
feature the small signal stages of the
amplifier are operated at higher supply voltages than the
amplifier’s high current output stage. +V
BOOST
(pin 11) and
–V
BOOST
(pin 12) are connected to the small signal circuitry of
the amplifier. +V
S
(pin 9,10) and –V
S
(pin 3,4) are connected to
the high current output stage. An additional 10V on the V
BOOST
pins is sufficient to allow the small signal stages to drive the
output transistors into saturation and improve the output voltage
swing for extra efficient operation when required. When close
swings to the supply rails is not required the +V
BOOST
and +V
S
pins must be strapped together as well as the –V
BOOST
and –V
S
pins. The boost voltage pins must not be at a voltage lower
than the V
S
pins.
This data sheet has been carefully checked and is believed to be reliable,
SHANNON ROAD •
is assumed
ARIZONA 85741 •
omissions. All specifications are subject
1 (800) 546-2739
APEX MICROTECHNOLOGY CORPORATION • 5980 NORTH
however, no responsibility
TUCSON,
for possible inaccuracies or
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to change without notice.
4
PA50U REV D JANUARY 2005 © 2005 Apex Microtechnology Corp.
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