ADA4310 AD [Analog Devices], ADA4310 Datasheet - Page 10

• Manufacturer Part Number: ADA4310
• Description: Low Cost, Dual, High Current Output Line Driver with Shutdown
• Manufacturer: AD [Analog Devices]

ADA4310-1
THEORY OF OPERATION
The ADA4310-1 is a current feedback amplifier with high
output current capability. With a current feedback amplifier, the
current into the inverting input is the feedback signal, and the
open-loop behavior is that of a transimpedance, dV
The open-loop transimpedance is analogous to the open-loop
voltage gain of a voltage feedback amplifier. Figure 20 shows a
simplified model of a current feedback amplifier. Because R
proportional to 1/g
where g
analysis of the follower with gain circuit yields
where:
G
R
IN
= 1
=
V
V
+
IN
g
O
1
m
R
R
m
G
is the transconductance of the input stage. Basic
F
=
≈
G
50
×
Ω
T
Z
( )
m
s
, the equivalent voltage gain is just T
+
T
G
Z
×
( )
s
R
IN
+
R
F
O
/dI
IN
Z
or T
× g
IN
Rev. 0 | Page 10 of 16
m
is
Z
,
.
Because G × R
amplifier has relatively constant bandwidth vs. gain, the 3 dB
point being set when |T
Of course, for a real amplifier there are additional poles that
contribute excess phase, and there is a value for R
the amplifier is unstable. Tolerance for peaking and desired
flatness determines the optimum R
V
IN
IN
R
R
G
N
<< R
Figure 20. Simplified Block Diagram
F
for low gains, a current feedback
Z
| = R
I
R
F
IN
.
IN
R
T
F
Z
F
in each application.
F
V
OUT
below which