BUF04

REV. 0

–12–

Operation Within an Op Amp Feedback Loop

The BUF04 is well suited as a current booster or isolation

buffer within the closed loop of precision op amps such as the

OP177, the OP97, the OP27, or the OP77. Since the BUF04 is

a closed loop voltage buffer, no interstage coupling resistor

between the op amp and the buffer’s input is required for circuit

stability. The wide bandwidth and high slew rate of the BUF04

assure that the loop has the characteristics of the op amp; hence,

no additional rolloff is required.

BUF04

6

3

500

Ω

OP177

3

R2

R1

100

2

1000pF

6

GAIN

10

100

1000

R2 (k

Ω)

1

10

100

Figure 38. BUF04 as Booster Stage for a Precision Op Amp

Paralleling BUF04s for Increased Load Drive Capability

In applications where continuous output currents greater than

50 mA are required or where heat management is an issue, a

number of BUF04s can be connected in parallel to reduce the

drive requirement of any one buffer. An example of one such

application is illustrated in Figure 39. In this circuit, the

BUF04s are required to drive a doubly terminated 50

Ω line to

±5 V. This type of a load for a single BUF04 would certainly

cause a power dissipation problem. Parallel operation results in

lower input and output impedances and increased bias currents;

on the other hand, input equivalent noise voltage is reduced and

input offset voltage remains unchanged.

±10V

50

Ω

3

R3

100

Ω

R1

47

Ω

6

BUF04

50

Ω

3

R2

47

Ω

6

BUF04

±5V

R4

100

Ω

Figure 39. Paralleling BUF04s for High Output Currents

Overdrive Recovery and Phase Reversal

In applications where the inputs could be driven to the supply

rails, the BUF04 recovers in 10 ns from positive or negative

overdrive. The BUF04 does not exhibit any output voltage

phase reversal when the input signal exceeds its input voltage

range.