TYPICAL PERFORMANCE CURVES
(CONT)
At T
CASE
= +25°C, V
S
=
±35V,
unless otherwise noted.
SMALL SIGNAL RESPONSE
G = 3, C
L
= 1nF
200MV/div
5V/div
2µs/div
APPLICATIONS INFORMATION
Figure 1 shows the OPA544 connected as a basic non-
inverting amplifier. The OPA544 can be used in virtually
any op amp configuration. Power supply terminals should be
bypassed with low series impedance capacitors. The tech-
nique shown, using a ceramic and tantalum type in parallel
is recommended. Power supply wiring should have low
series impedance and inductance.
+35V
V+
10µF
+
0.1µF
R
1
5kΩ
R
2
10kΩ
G = 1+
The safe output current decreases as V
S
–V
O
increases. Output
short-circuits are a very demanding case for SOA. A short-circuit
to ground forces the full power supply voltage (V+ or V–) across
the conducting transistor. With V
S
=
±35V
the safe output current
is 1.5A (at 25˚C). The short-circuit current is approximately 4A
which exceeds the SOA. This situation will activate the thermal
shutdown circuit in the OPA544. For further insight on SOA,
consult Application Bulletin AB-039.
SAFE OPERATING AREA
10
Current-Limited
T
C
= 25°C
Output current may
be limited to less
than 4A—see text.
T
C
= 85°C
0.4
T
C
= 125°C
4
Output Current (A)
Z
L
R
2
=3
R
1
1
OPA544
V
O
V
IN
0.1µF
10µF
+
0.1
1
2
5
10
|V
S
– V
O
| (V)
20
50
100
FIGURE 2. Safe Operating Area.
CURRENT LIMIT
The OPA544 has an internal current limit set for approxi-
mately 4A. This current limit decreases with increasing
junction temperature as shown in the typical curve, Current
Limit vs Temperature. This, in combination with the thermal
shutdown circuit, provides protection from many types of
overload. It may not, however, protect for short-circuit to
ground, depending on the power supply voltage, ambient
temperature, heat sink and signal conditions.
V–
–35V
FIGURE 1. Basic Circuit Connections.
SAFE OPERATING AREA
Stress on the output transistors is determined by the output
current and the voltage across the conducting output transis-
tor, V
S
–V
O
. The power dissipated by the output transistor is
equal to the product of the output current and the voltage
across the conducting transistor, V
S
–V
O
. The Safe Operating
Area (SOA curve, Figure 2) shows the permissible range of
voltage and current.
®
OPA544
6
TI [ TEXAS INSTRUMENTS ]
