R

R

1

2

OPA551

OPA551

“SLAVE”

“MASTER”

V

IN

R

S

(1)

10Ω

R

S

(1)

10Ω

R

L

NOTE: (1) R

S resistors minimize the circulating

current that can flow between the two devices

due to V

OS errors.

R

F

4kΩ

C

S

1.8nF

10nF

OPA551

+30V

–30V

V

I

C

F

220pF

R

G

4kΩ

OPA551, OPA552

SBOS100B – JULY 1999 – REVISED JANUARY 2016

www.ti.com

Typical Application (continued)

8.2.2 Detailed Design Procedure

8.2.2.1 Capacitive Loads

The dynamic characteristics of the OPA55x have been optimized for commonly-encountered gains, loads, and

operating conditions. The combination of low closed-loop gain and capacitive load decreases the phase margin

and may lead to gain peaking or oscillations. Figure 28 shows a circuit that preserves phase margin with a 10-nF

capacitive load. Figure 33 shows the small-signal step response for the circuit in Figure 28. Consult SBOA015 for

more information.

Figure 28. Driving Large Capacitive Loads

8.2.2.2 Increasing Output Current

In those applications where the 200 mA of output current is not sufficient to drive the desired load, output current

can increase by connecting two or more OPA551s or OPA552s in parallel, as shown in Figure 29. Amplifier A1 is

the master amplifier and may be configured in virtually an operational amplifier circuit. Amplifier A2, the slave, is

configured as a unity-gain buffer. Alternatively, external output transistors can be used to boost output current.

The circuit in Figure 30 is capable of supplying output currents up to 1 A. Alternatively, consider the OPA547,

OPA548, and OPA549 series power operational amplifiers for high output current drive, along with programmable

current limit and output disable capability.

Figure 29. Parallel Amplifiers Increase Output Current Capability

14

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