AD600/AD602
C1LO
A1HI
A1LO
GAT1
GAT2
A2LO
A2HI
C2LO
0dB ADJUST
|
|
|
|
|
|
1 |
|
|
|
| 16 |
|
|
|
|
|
|
2 |
|
| A1 | 15 | |
|
|
|
| ||
|
| ||||
3 |
|
|
|
| 14 |
|
|
|
|
|
|
|
|
|
|
|
|
4 |
|
| REF |
| 13 |
|
|
|
|
| |
|
|
|
|
| |
5 |
|
|
|
| 12 |
|
|
|
|
|
|
6 |
|
| A2 | 11 | |
|
|
|
| ||
|
| ||||
7 |
|
|
|
| 10 |
|
|
|
|
|
|
|
|
|
|
|
|
8 | U1 AD600 | 9 | |||
|
| ||||
C1HI |
|
A1CM | C1 |
| |
A1OP | 0.1∝F |
VPOS
+6V DEC
R1
VNEGΩ
A2OP
A2CM
C2HI
R2
100Ω
U3A
1/4
AD713
C2 R5
0.1∝FΩ
5.36k
R4 C3 
133kΩ 0.001∝F
C1LO
A1HI
A1LO
GAT1
GAT2
A2LO
A2HI
U3B
C2LO
1/4
AD713
1 | 16 | C1HI |
|
|
|
|
| ||
2 | 15 | A1CM | C4 |
|
| VOUT | |||
A1 | 14 | A1OP | 2∝F | |
3 |
|
|
| |
4 | 13 | VPOS | +6V DEC |
|
|
| |||
REF | 12 | VNEG |
| |
5 |
|
| ||
6 | 11 | A2OP |
|
|
A2 | 10 | A2CM |
|
|
7 |
|
| ||
|
|
| ||
8 | 9 | C2HI |
|
|
|
|
|
U2 AD600
R3 |
|
|
|
|
| +6V |
|
|
|
|
|
|
|
R17 | INPUT |
|
|
|
| R6 |
| R7 | R8 | R9 | R16 |
| |
200Ω |
|
|
|
|
|
| |||||||
115Ω |
|
|
|
| 3.4kΩ |
| 1kΩ | 294Ω | 1kΩ | 287Ω |
| ||
|
|
|
|
|
|
| |||||||
|
|
|
|
|
| C5 |
|
|
|
|
|
| +6V |
|
|
|
|
|
| 22∝F |
|
|
|
|
| ||
|
|
|
|
|
|
|
|
|
|
|
| ||
|
|
|
|
|
|
|
|
|
|
| +6V DEC |
| |
|
|
|
|
|
|
|
|
|
|
|
|
| FB |
|
|
|
|
|
|
|
|
|
|
|
|
| 0.1∝F |
|
|
|
|
|
|
|
|
|
|
|
|
| +6V DEC |
|
|
|
|
| 1 | VINP | VPOS | 14 |
|
|
|
|
|
|
|
|
| NC | 2 | U4 |
| 13 | NC |
|
|
| |
|
|
|
| AD636 |
| R11 |
| ||||||
|
|
|
|
|
| 0.1∝F | |||||||
|
|
|
|
|
|
|
|
|
| ||||
|
|
|
|
|
|
|
|
|
|
| 56.2kΩ |
| |
|
|
|
| 3 | VNEG |
| 12 | NC |
|
| FB | ||
|
|
|
|
|
|
|
|
| |||||
|
|
|
|
| 4 | CAVG |
| 11 | NC | R10 |
| C6 |
|
|
|
|
|
|
| 4.7∝F |
| ||||||
|
|
|
|
|
| 3.16kΩ | |||||||
|
|
|
|
|
|
|
|
|
| ||||
|
|
|
|
|
|
|
|
|
|
|
| ||
|
|
|
| NC | 5 | VLOG | COMM | 10 |
|
|
|
| POWER SUPPLY |
|
|
|
| NC | 6 | BFOP | LDLO | 9 |
|
|
|
| DECOUPLING NETWORK |
|
|
|
|
|
|
|
|
| |||||
|
| +6V DEC |
|
| 7 | BFIN | VRMS | 8 |
|
| U3C | VLOG | |
|
|
|
|
|
|
| |||||||
|
| R15 |
|
|
|
|
|
|
|
|
| 1/4 |
|
|
| 5.11kΩ |
|
|
|
|
|
|
| +316.2mV |
| AD713 |
|
|
| R14 | R13 | R12 |
|
|
|
|
|
| NC = NO CONNECT |
| |
|
| 7.32kΩ | 866Ω | 1kΩ |
|
|
|
|
|
|
| ||
|
|
|
|
|
|
|
|
|
|
| |||
Figure 29. 120 dB Dynamic Range RMS Responding Circuit Optimized for S/N Ratio
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
VLOG to read 0 dB when VIN 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 and at the same time center the dy- namic range at 60 dB, which occurs if the VG of U1B is equal to zero. These arrangements ensure that the VLOG will still fit within the ± 6 V supplies.
Figure 30 shows VLOG to be linear over a full 120 dB range. Figure 31 shows the error ripple due to the individual gain func- tions which is bounded by ± 0.2 dB (dotted lines) from 6 μV to 2 V. The small perturbations at about 200 μV and 20 mV, caused by the impracticality of matching the gain functions per- fectly, are the only sign that the gains are now sequential. Fig-
ure 32 is a plot of VAGC which remains very close to its set value of 316 mV rms over the full 120 dB range.
To more directly compare the
| 5 |
|
|
|
|
|
|
|
|
|
|
| |
Volts– | 4 |
|
|
|
|
|
2 |
|
|
|
|
| |
| 3 |
|
|
|
|
|
OUTPUT | 1 |
|
|
|
|
|
|
|
|
|
|
| |
LOGARITHMIC | 0 |
|
|
|
|
|
|
|
|
|
| ||
|
|
|
|
|
| |
|
|
|
|
|
| |
|
|
|
|
|
| |
|
|
|
|
|
| |
|
|
|
|
|
| |
| 1∝V | 10∝V 100∝V 1mV 10mV 100mV | 1V | 10V | ||
INPUT SIGNAL – V RMS
Figure 30. VLOG Is Essentially Linear Over the Full 120 dB Range
ratio relative to 0 dBV, this being almost the maximum output capability of the AD600. Results for the simultaneous mode can be seen in Figure 33. The S/ N ratio degreades uniformly as the gain is increased. Note that since the inverting gain control was used, the gain in this curve and in Figure 34 decreases for more positive values of the
| REV. A |
