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AD600 Datasheet PDF : 32 Pages
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AD600/AD602
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.
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.
85
80
75
70
65
60
55
50
45
40
35
30
–0.5
0
0.5
1.0
1.5
2.0
2.5
3.0
VG
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
–40.00dB
A2
–41.07dB
INPUT
0dB
VC = 0V
–40.00dB
C1HI C1LO
41.07dB
VG1
VO1 = 0.592V
1.07dB
–42.14dB
C2HI C2LO
41.07dB
VG2
VO2 = 1.908V
OUTPUT
0dB
Figure 23. AD600 Gain Control Input Calculations for Sequential Control Operation (A)
A1
–0.51dB
A2
–1.07dB
INPUT
0dB
–0.51dB
C1HI C1LO
41.07dB
40.56dB
–41.63dB
C2HI C2LO
41.07dB
VC = 1.25V
VG1
VO1 = 0.592V
VG2
VO2 = 1.908V
Figure 24. AD600 Gain Control Input Calculations for Sequential Control Operation (B)
OUTPUT
40dB
A1
0dB
A2
38.93dB
INPUT
0dB
0dB
C1HI C1LO
41.07dB
41.07dB
–2.14dB
C2HI C2LO
41.07dB
VC = 2.5V
VG1
VO1 = 0.592V
VG2
VO2 = 1.908V
Figure 25. AD600 Gain Control Input Calculations for Sequential Control Operation (C)
OUTPUT
80dB
Rev. F | Page 12 of 32
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