参数资料
型号: PA228A
英文描述: Operational Amplifier
中文描述: 运算放大器
文件页数: 4/5页
文件大小: 69K
代理商: PA228A
OPERATING
CONSIDERATIONS
PA28/29
PA28A/29A
GENERAL
Please read Application Note 1 "General Operating Consid-
erations" which covers stability, supplies, heat sinking, mount-
ing, current limit, SOA interpretation, and specification inter-
pretation. Visit www.apexmicrotech.com for design tools that
help automate tasks such as calculations for stability, internal
power dissipation, current limit and heat sink selection. The
"Application Notes" and "Technical Seminar" sections contain
a wealth of information on specific types of applications. Pack-
age outlines, heat sinks, mounting hardware and other acces-
sories are located in the "Packages and Accessories" section.
Evaluation Kits are available for most Apex product models,
consult the "Evaluation Kit" section for details. For the most
current version of all Apex product data sheets, visit
www.apexmicrotech.com.
SAFE OPERATING AREA (SOA)
The SOA curves combine the effect of all limits for this power
op amp. For a given application, the direction and magnitude
of the output current should be calculated or measured and
checked against the SOA curves. This is simple for resistive
loads but more complex for reactive and EMF generating
loads.
NOTE: For protection against sustained, high energy flyback,
external fast-recovery diodes should be used.
MONOLITHIC AMPLIFIER
STABILITY CONSIDERATIONS
All monolithic power op amps use output stage topologies
that present special stability problems. This is primarily due to
non-complementary (both devices are NPN) output stages
with a mismatch in gain and phase response for different
polarities of output current. It is difficult for the op amp manu-
facturer to optimize compensation for all operating conditions.
The recommended R-C network of 1 ohm in series with
0.1
μ
F from output to AC common (ground or a supply rail, with
adequate bypass capacitors) will prevent local output stage
oscillations.
ADDITIONAL PA29 PIN FUNCTIONS
V
BOOST
The V
pin is the positive terminal for the load of the
second stage of the amplifier. When that terminal is connected
to a voltage greater than +V
it will provide more drive to the
upper output transistor, which is a darlington connected emit-
ter follower. This will better saturate the output transistor.
When V
is about 5 Volts greater than +V
the positive
output can swing 0.5 Volts closer to the rail. This is as much
improvement as is possible.
V
pin requires approximately 4-6mA of current. Dy-
namically it represents 1K
impedance. The maximum volt-
age that can be applied to V
is 40 volts with respect to
V
S
. There is no limit to the difference between +V
S
and V
BOOST
.
IN
+IN
V
S
R
S
I
SENSE
OUT
V
BOOST
+V
S
FIGURE 2. PA29 EQUIVALENT SCHEMATIC (ONE CHANNEL)
5
4
3
2
11
SUPPLY TO OUTPUT DIFFERENTIAL VOLTAGE, Vs
Vo(V)
2
3
4
5
10
20
30 40
O
EACH ONELOADED
EACH BOHLOADED
SOA
THERMAL CONSIDERATIONS
Although R
is the same for PA28/29 there are differences
in the thermal interface between case and heatsink which will
limit power dissipation capability. Thermal grease or an Apex
TW03 thermal washer, R
= .1-.2
°
C/W, is the only recom-
mended interface for the PA28. The PA29 may require a
thermal washer which is electrically insulating since the tab is
tied to
V
. This can result in thermal impedances for R
θ
CS
of
up to 1
°
C/W or greater.
APEX MICROTECHNOLOGY CORPORATION
5980 NORTH SHANNON ROAD
TUCSON, ARIZONA 85741
USA
APPLICATIONS HOTLINE: 1 (800) 546-2739
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