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6

OPA544

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.

short-circuits are a very demanding case for SOA. A short-circuit

to ground forces the full power supply voltage (V+ or V–) across

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

Stress on the output transistors is determined by the output

current and the voltage across the conducting output transis-

equal to the product of the output current and the voltage

Area (SOA curve, Figure 2) shows the permissible range of

voltage and current.

FIGURE 1. Basic Circuit Connections.

At T

5V/div

G = 1+

= 3

R

2

R

1

+

Z

L

V

O

R

2

10k

Ω

R

1

5k

Ω

0.1µF

10µF

OPA544

V–

–35V

+35V

V+

V

IN

+

10µF

0.1µF

200MV/div

SMALL SIGNAL RESPONSE

G = 3, C

2µs/div

FIGURE 2. Safe Operating Area.

12

5

10

|V

(V)

20

50

100

SAFE OPERATING AREA

10

4

1

0.4

0.1

Current-Limited

T

T

T

Output current may

be limited to less

than 4A—see text.

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.