Datasheet

ADA4862-3
Rev. A | Page 11 of 16
APPLICATIONS
USING THE ADA4862-3 IN GAINS = +1, −1
The ADA4862-3 was designed to offer outstanding video
performance, simplify applications, and minimize board area.
The ADA4862-3 is a triple amplifier with on-chip feedback and
gain set resistors. The gain is fixed internally at G = +2. The
inclusion of the on-chip resistors not only simplifies the design
of the application but also eliminates six surface-mount
resistors, saving valuable board space and lowers assembly
costs. A typical schematic is shown in
Figure 29.
0.01μF
0.01μF
V
IN
R
T
V
OUT
+V
S
–V
S
GAIN OF +2
05600-029
10μF
10μF
Figure 29. Noninverting Configuration (G = +2)
While the ADA4862-3 has a fixed gain of G = +2, it can be used
in other gain configurations, such as G = −1 and G = +1, which
are discussed next.
Unity-Gain Operation (Option 1)
There are two options for obtaining unity gain (G = +1). The
first is shown in
Figure 30. In this configuration, the –IN input
pin is left floating (feedback is provided via the internal 550 Ω),
and the input is applied to the noninverting input. The noise
gain for this configuration is 1. Frequency performance and
transient response are shown in
Figure 31 through Figure 33.
0.01μF
10μF
10μF
0.01μF
V
IN
R
T
V
OUT
+V
S
–V
S
GAIN OF +1
05600-032
Figure 30. Unity Gain of Option 1
4
–4
0.1 1000
FREQUENCY (MHz)
CLOSED-LOOP GAIN (dB)
05600-053
1 10 100
3
2
1
0
–1
–2
–3
G = +1
R
L
= 150Ω
C
L
= 4pF
V
OUT
= 200mV p-p
V
S
= ±5V
V
S
= +5V
Figure 31. Small Signal Unity Gain
3
–6
0.1 1000
FREQUENCY (MHz)
CLOSED-LOOP GAIN (dB)
05600-002
1 10 100
2
1
0
–1
–2
–3
–4
–5
V
S
= +5V
V
S
= ±5V
G = +1
R
L
= 150Ω
C
L
= 4pF
V
OUT
= 2V p-p
Figure 32. Large Signal Gain +1
2.0
–2.0
OUTPUT VOLTAGE (V)
1.5
1.0
0.5
0
–0.5
–1.0
–1.5
C
L
= 4pF
C
L
= 9pF
C
L
= 6pF
G = +1
R
L
= 150Ω
V
OUT
= 2V p-p
V
S
= ±5V
TIME = 5ns/DIV
05600-020
Figure 33. Large Signal Transient Response for Various Capacitor Loads