AD600 查看數據表（PDF） - Analog Devices
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AD600 Datasheet PDF : 20 Pages
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AD600/AD602
INPUT
1V RMS
MAX
(SINE WAVE)
C1LO 1
A1HI 2
A1LO
3
GAT1
4
GAT2
5
A2LO 6
A2HI
7
C2LO 8
A1
REF
A2
U1 AD600
C1HI
16
A1CM
15
A1OP
14
VPOS
13
VNEG
12
11 A2OP
10 A2CM
C2HI
9
C1
0.1µF
+5V DEC
–5V DEC
R1
133kΩ
U3A
R2
487Ω
R3
200Ω
1/4
AD713
C2
0.1µF
R5
1.58kΩ
R4
133kΩ
C3
220pF
U3B
1/4
AD713
C1LO 1
C1HI
16
A1HI 2
A1CM
15
C4
A1LO
A1
A1OP
2µF
3
14
GAT1
4
GAT2
5
VPOS
13
REF
VNEG
12
+5V DEC
–5V DEC
A2LO 6
A2HI
7
11 A2OP
A2
10 A2CM
C2LO 8
C2HI
9
U2 AD600
VOUT
+5V
FB
+5V DEC
0.1µF
–5V DEC
FB
0.1µF
–5V
POWER SUPPLY
DECOUPLING NETWORK
–2dB
–62.5mV 0dB
+2dB
+62.5mV
–5V
+5V
R6
R7
R8
R9
10kΩ 127Ω 127Ω 10kΩ
C5
22µF
+5V DEC
+5V DEC
R15
19.6kΩ
Q1
2N3906
R14
301kΩ
R16
6.65kΩ
R13
3.01kΩ
R12
11.3kΩ
1 VINP
VPOS 14
U4
NC 2 AD636
13 NC
–5V DEC
3 VNEG
12 NC
4 CAVG
NC 5 VLOG
11 NC R10
3.16kΩ
COMM 10
R11
46.4kΩ
C6
4.7µF
NC 6 BFOP LDLO 9
7 BFIN
VRMS 8
U3C
+316.2mV
1/4
AD713
NC = NO CONNECT
VLOG
Figure 25. RMS Responding AGC Circuit with 100 dB Dynamic Range
100 dB to 120 dB RMS Responding Constant Bandwidth AGC
Systems with High Accuracy dB Outputs
The next two applications double as both AGC amplifiers and
measurement systems. In both, precise gain offsets are used to
achieve either (1) a very high gain linearity of ± 0.1 dB over the
full 100 dB range, or (2) the optimal signal-to-noise ratio at any
gain.
A 100 dB RMS/AGC System with Minimal Gain Error
(Parallel Gain with Offset)
Figure 25 shows an rms-responding AGC circuit, which can
equally well be used as an accurate measurement system. It
accepts inputs of 10 µV to 1 V rms (–100 dBV to 0 dBV) with
generous overrange. Figure 26 shows the logarithmic output,
VLOG, which is accurately scaled 1 V per decade, that is,
50 mV/dB, with an intercept (VLOG = 0) at 3.16 mV rms
(–50 dBV). Gain offsets of ± 2 dB have been introduced between
the amplifiers, provided by the ± 62.5 mV introduced by R6–R9.
These offsets cancel a small gain ripple which arises in the
X-AMP from its finite interpolation error, which has a period of
18 dB in the individual VCA sections. The gain ripple of all
three amplifier sections without this offset (in which case the
gain errors simply add) is shown in Figure 27; it is still a
remarkably low ± 0.25 dB over the 108 dB range from 6 µV to
1.5 V rms. However, with the gain offsets connected, the gain
linearity remains under ± 0.1 dB over the specified 100 dB range
(Figure 28).
5
4
3
2
1
0
–1
–2
–3
–4
–5
1µV 10µV 100µV 1mV 10mV 100mV 1V
10V
INPUT SIGNAL – V RMS
Figure 26. VLOG Plotted vs. VIN for Figure 25‘s Circuit
Showing 120 dB AGC Range
–14–
REV. A
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