Datasheet

AD8352
Rev. B | Page 12 of 20
20
0
0 800
R
G
(Ω)
GAIN (dB)
18
16
14
12
10
8
6
4
2
100 200 300 400 500 600 700
05728-028
Figure 24. Gain vs. R
G
, R
L
= 1 kΩ
20
0
00
C
D
(pF)
.5
GAIN (dB)
18
16
14
12
10
8
6
4
2
0.1 0.2 0.3 0.4
05728-029
Figure 25. Gain vs. C
D
, R
L
= 1 kΩ
SINGLE-ENDED INPUT OPERATION
The AD8352 can be configured as a single-ended-to-differential
amplifier, as shown in Figure 26. To balance the outputs when
driving the VIP input, an external resistor (R
N
) of 200 Ω is added
between VIP and RGN. See Equation 2 to determine the single-
ended input gain (A
V Single-Ended
) for a given R
G
or R
L
.
30
430)53()5(
500
+
+
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
+++
+
=
−
L
L
L
L
G
G
EndedSingleV
R
R
R
RR
R
A
(2)
where
R
L
is the single-ended load.
R
G
is the gain setting resistor.
Figure 27 plots gain vs. R
G
for 200 Ω and 1 kΩ loads. Table 7
and Table 8 show the values of C
D
and R
D
required (for 180 MHz
broadband, third-order, single tone optimization) for 200 Ω and
1 kΩ loads, respectively. This single-ended configuration provides
−3 dB bandwidths similar to input differential drive. Figure 28
through Figure 31 show distortion levels at a gain of 12 dB for
both 200 Ω and 1 kΩ loads. Gains from 3 dB to 18 dB, using
optimized C
D
and R
D
values, obtain similar distortion levels.
R
D
R
G
25Ω
65Ω
50Ω
0.1µF
0.1µF
0.1µF
0.1µF
RGP
RGN
AD8352
A
C
C
D
VIP
R
N
200Ω
05728-024
Figure 26. Single-Ended Schematic
40
0
1 10k
R
G
(Ω)
GAIN (dB)
10 100 1k
35
30
25
20
15
10
5
GAIN, R
L
=1kΩ
GAIN, R
L
=200Ω
05728-020
Figure 27. Gain vs. R
G
–
60
–110
FREQUENCY (MHz)
HD2 (dBc)
10 70 140 190 240
–70
–80
–90
–100
2V p-p OUT
1V p-p OUT
05728-021
Figure 28. Single-Ended, Second-Order Harmonic Distortion (HD2) vs.
Frequency, 200 Ω Load