BUF04 Datasheet, PDF (12/16 Pages) Analog Devices – Closed-Loop High Speed Buffer

BUF04
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.
R1
100
R2
2
V_IN
6
OP177
3
3
BUF04
6
R_L
V_OUT
C_L
500Ω 1000pF
GAIN R2 (kΩ)
10
1
100
10
1000
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.
V_IN
±10V
R1
R3
47Ω
3
BUF04
6
100Ω
R_S
R2
R4
50Ω
47Ω ₃
6 ^100Ω
BUF04
±5V
V_OUT
R_L
50Ω
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.
–12–
REV. 0