This data sheet has been carefully checked and is believed to be reliable, however, no responsibility is assumed for possible inaccuracies or omissions. All specifications are subject to change without notice.
PA93U REV. B MARCH 1999
1999 Apex Microtechnology Corp.
OPERATING
CONSIDERATIONS
PA93
SUPPLY TO OUTPUT DIFFERENTIAL, V
S
– V
O
(V)
10
20
30 40
100
200
300
500
O
S
S
,
.1
.08
.6
.4
.3
.2
.8
3
2
1
4
6
8
20
10
DCT
C
=125
°
C
100mS
60 80
200mS
DC, T
C
= 25
°
C
DCT
C
=85
°
C
GENERAL
Please read the “General Operating Considerations” sec-
tion, which covers stability, supplies, heatsinking, mounting,
current limit, SOA interpretation, and specification interpreta-
tion. Additional information can be found in the application
notes. For information on the package outline, heatsinks, and
mounting hardware, consult the “Accessory and Package
Mechanical Data” section of the handbook.
CURRENT LIMIT
For proper operation, the current limit resistor (R
) must be
connected as shown in the external connection diagram. For
optimum reliability the resistor value should be set as high as
possible. The value is calculated as follows; with the maximum
practical value of 16 ohms.
.65
R
CL
=
I
LIM
SAFE OPERATING AREA (SOA)
The MOSFET output stage of this power operational ampli-
fier has two distinct limitations:
1. The current handling capability of the MOSFET geometry
and the wire bonds.
2. The junction temperature of the output MOSFETs.
NOTE: The output stage is protected against transient flyback.
However, for protection against sustained, high energy flyback,
external fast-recovery diodes should be used.
SAFE OPERATING CURVES
The safe operating area curves define the maximum addi-
tional internal power dissipation the amplifier can tolerate
when it produces the necessary output to drive an external
load.
INPUT PROTECTION
Although the PA93 can withstand differential voltages up to
±
20V, additional external protection is recommended. Low
leakage, low capacitance JFETs connected as diodes are
recommended (e.g. 2N4416, Q1-Q4 in Figure 2). The differen-
tial input voltage will be clamped to
±
1.4V. This is sufficient
overdrive to produce maximum power bandwidth.
POWER SUPPLY PROTECTION
Unidirectional zener diode transient suppressors are recom-
mended as protection on the supply pins. See Figure 2. The
zeners clamp transients to voltages within the power supply
rating and also clamp power supply reversals to ground.
Whether the zeners are used or not, the system power supply
should be evaluated for transient performance including power-
on overshoot and power-off polarity reversals as well as line
regulation.
Conditions which can cause open circuits or polarity rever-
sals on either power supply rail should be avoided or protected
against. Reversals or opens on the negative supply rail is
known to induce input stage failure. Unidirectional transzorbs
prevent this, and it is desirable that they be both electrically and
physically as close to the amplifier as possible.
STABILITY
The PA93 is externally compensated and performance can
be tailored to the application. Use the graphs of small signal
response and power response as a guide. The compensation
capacitor C
must be rated at 500V working voltage. An NPO
capacitor is recommended. The compensation network C
R
C
must be mounted closely to the amplifier pins 4 and 5 to avoid
spurious oscillation.
QUIESCENT CURRENT REDUCTION
When pin 3 (I
) is shorted to pin 5 (CC2) the AB biasing of
the output stage is disabled. This lowers quiescent power but
also raises distortion since the output stage is then class C
biased. The output stage bias current is nominally set at 1mA.
Pin 3 may be left open if not used.
+V
S
–IN
+IN
Z1
Z2
11, 12
7, 8
1
2
6
PA93
Q1
Q2
–V
S
Q3
Q4
FIGURE 2.
OVERVOLTAGE
PROTECTION