Datasheet

AD600/AD602
SNR (dB)
85
45
35
40
60
50
55
65
70
75
80
There are several options in connecting the gain-control inputs.
The choice depends on the desired SNR and gain error (output
ripple). The following examples feature the AD600; the
arguments generally apply to the AD602, with appropriate
changes to the gain values.
V
G
30
3.00–0.5 2.52.01.51.00.5
00538
SEQUENTIAL MODE (MAXIMUM SNR)
In the sequential mode of operation, the SNR is maintained at
its highest level for as much of the gain control range as
possible, as shown in Figure 22. Note here that the gain range is
0 dB to 80 dB. Figure 23, Figure 24, and Figure 25 show the
general connections to accomplish this. Both gain-control
inputs, C1HI and C2HI, are driven in parallel by a positive-only,
ground-referenced source with a range of 0 V to 2.5 V.
-022
V
O2
= 1.908V
Figure 22. SNR vs. Control Voltage Sequential Control (1 MHz Bandwidth)
An auxiliary amplifier that senses the voltage difference
between input and output commons is provided to reject this
common voltage.
A1
Rev. F | Page 12 of 32
41.07dB
INPUT
0dB
–40.00dB
–40.00dB
C1HI C1LO
1.07dB
V
G2
OUTPUT
0dB
–41.07dB
–42.14dB
C2HI C2LO
41.07dB
A2
V
O1
= 0.592V
V
G1
V
C
= 0V
00538-023
–0.51dB
OUTPUT
Figure 23. AD600 Gain Control Input Calculations for Sequential Control Operation (A)
A1
40dB
41.07dB
–0.51dB
C1HI C1LO
–1.07dB
–41.63dB
40.56dB
41.07dB
C2HI C2LO
A2
INPUT
38.93dB
V
O2
= 1.908V
V
G2
V
O1
= 0.592V
V
G1
0dB
V
C
= 1.25V
00538-055
Figure 24. AD600 Gain Control Input Calculations for Sequential Control Operation (B)
A1
0dB
0dB
41.07dB
C1HI C1LO
–2.14dB
41.07dB
41.07dB
C2HI C2LO
A2
INPUT
OUTPUT
80dB
0dB
V
C
= 2.5V
V
O1
= 0.592V
V
G1
V
O2
= 1.908V
V
G2
00538-056
Figure 25. AD600 Gain Control Input Calculations for Sequential Control Operation (C)