AD600/AD602
INPUT
0dB
VC = 0V
INPUT
0dB
VC = 1.25V
INPUT
0dB
VC = 25V
A1
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41.07dB | 1.07dB | |||
C1HI | C1LO | |||
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| VG1 |
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| VO1 = 0.592V |
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41.07dB | 40.56dB | |||
C1HI | C1LO | |||
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| VG1 |
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| VO1 = 0.592V |
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| (b) | |
| 0dB |
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| 0dB | 41.07dB | 41.07dB | |
C1HI | C1LO | |||
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VG1
VO1 = 0.592V
(c)
A2
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| OUTPUT |
| 41.07dB | |||
| 0dB | |||
C1HI | C1LO |
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| VG2 |
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| VO2 = 1.908V |
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| OUTPUT |
| 41.07dB | |||
| 40dB | |||
C1HI | C1LO |
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| VG2 |
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| VO2 = 1.908V |
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| 38.93dB |
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| OUTPUT |
| 41.07dB | |||
| 80dB | |||
C1HI | C1LO |
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VG2
VO2 = 1.908V
Figure 3. AD600 Gain Control Input Calculations for Sequential Control Operation
The gains are offset (Figure 4) such that A2’s gain is increased only after A1’s gain has reached its maximum value. Note that for a differential input of
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| Gain (dB) = 32 VC |
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where VC is the applied control voltage. |
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| +41.07dB |
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| 40.56dB |
| +38.93dB | |
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| A1 |
| A2 |
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| 20dB |
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+1.07dB |
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| 0.592 |
| 1.908 |
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GAIN |
| 0 | 0.625 | 1.25 | 1.875 | 2.5 | VC (V) | |
0 | 20 | 40 | 60 | 80 | 82.14 | |||
(dB) | ||||||||
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*GAIN OFFSET OF 1.07dB, OR 33.44mV
Figure 4. Explanation of Offset Calibration for Sequential Control
When VC is set to zero, VG1 =
A2 is
Parallel Mode (Simplest
In this mode, the
Low Ripple Mode (Minimum Gain Error)
As can be seen in Figures 6 and 7, the output ripple is periodic. By offsetting the gains of Al and A2 by half the period of the ripple, or 3 dB, the residual gain errors of the two amplifiers can be made to cancel. Figure 9 shows the much lower gain rip ple when configured in this manner. Figure 10 plots the S/N ratio as a function of gain; it is very similar to that in the “Par- allel Mode.”
REV. A |