Datasheet
AD600/AD602
Rev. F | Page 24 of 32
Figure 51 shows the circuit for the sequential control scheme.
R6 to R9 with R16 provide offsets of 42.14 dB between the
individual amplifiers to ensure smooth transitions between the
gain of each successive X-AMP, with the sequence of gain
increase being U1A, then U1B, and then U2A. The adjustable
attenuator provided by R3 + R17 and the 100 input resistance
of U1A, as well as the fixed 6 dB attenuation provided by R2
and the input resistance of U1B, are included both to set V
LOG
to
read 0 dB when V
IN
is 3.16 mV rms and to center the 100 dB
range between 10 µV rms and 1 V rms input. R5 and C3
provide a 3 dB noise bandwidth of 30 kHz. R12 to R15 change
the scaling from 625 mV/decade at the control inputs to
1 V/decade at the output. At the same time, R12 to R15 center
the dynamic range at 60 dB, which occurs if the V
G
of U1B is
equal to 0. These arrangements ensure that the V
LOG
still fits
within the ±6 V supplies.
R14
7.32kΩ
R15
5.11kΩ
+6V DEC
R13
866Ω
C1HI
A1CM
A1OP
VPOS
C1LO
A1HI
A1LO
GAT1
VNEG
A2OP
A2CM
C2HI
GAT2
A2LO
A2HI
C2LO
+6V
DEC
–6V
DEC
–6V
DEC
NC
NC
C5
22µF
+6V DEC
R11
56.2kΩ
R10
3.16kΩ
U3C
U3A
1/4
AD713
C2
0.1µF
NC = NO CONNECT
R6
3.4kΩ
R8
294Ω
+6V
C1HI
A1CM
A1OP
VPOS
C1LO
A1HI
A1LO
GAT1
VNEG
A2OP
A2CM
C2HI
GAT2
A2LO
A2HI
C2LO
C4
2µF
C1
0.1µF
C3
0.001µF
R4
133kΩ
R5
5.36kΩ
133kΩ
R2
100Ω
R1
C6
4.7µF
+316.2mV
1
2
3
4
5
6
7
14
13
12
11
10
9
8
U4
AD636
FB
FB
+6V
–6V
+6V
DEC
–6V
DEC
0.1µF
0.1µF
POWER SUPPLY
DECOUPLING
NETWORK
U3B
1/4
AD713
1
2
3
16
15
14
4
5
6
7
8
13
12
11
10
9
REF
A1
A2
+
–
V
OUT
+5V
+
–
U2 AD600
DEC
–5V
DEC
1/4
AD713
V
LOG
R7
1kΩ
R16
287Ω
R9
1kΩ
R17
115Ω
R3
200Ω
0dB
ADJUST
1
2
3
16
15
14
4
5
6
7
8
13
12
11
10
9
REF
INPUT
A1
A2
+
–
+
–
U1 AD600
R12
1kΩ
00538-049
V
IN
–V
S
C
AV
dB
BUF OUT
BUF IN
NC
+V
S
COM
R
L
I
OUT
NC
NC
NC
Figure 51. 120 dB Dynamic Range RMS Responding Circuit Optimized for SNR