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Fri Jan 7 20:08:39 EST 2011
RC-decay envelope, FET controlled?
RST o---------------------o------o
__| |
R1 || |
PWM o--/\/\/\--o------|| =====
| ||__ | C2
| | |
===== | |
| C1 | |
| | |
o----------o------O
Principle: resistance modulation. RST is mostly for resetting and
possibly voltage feedback, i.e. ADC or 1/2 time CMOS trigger.
In general a FET resistor like this is nonlinear but it is possible to
linearize using a simple voltage divider. This sounds nice, but hase
some problems:
- Very sensitive to V_T for low condictivity (high resistance)
- Linear, while we need exponential range.
- V_DS needs to be less than the V-V_T distance, which means we
can't have a large resistance combined with a large signal.
This looks like it's a show stopper.
[1] http://graffiti.virgin.net/ljmayes.mal/comp/vcr.htm
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