Everybody has seen this classic oscillator design using NAND gates (or invertors).
+-=NAND---+-=NAND--+ | R C +---------+--------+I have to figure out how to mod this cct to react to an external waveform G for the following circuit output.
Condition Output Gf>fosc = G wave Gf=
At the very least, it sounds like you need a frequency comparison, which means sequential logic. An AND or XOR gate makes a basic phase detector (good for 180 degrees), and a flip-flop (fed runt trigger pulses) makes an even better one.
If you're keen, you might do it within a cycle. If you're not (or it doesn't matter much), you can filter it and do analog comparison. Or use F-V converters or something.
Tim
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That's something to think about. Thanks..
It's one of those electronics problems where just defining the problem is a problem :P
D from BC
Welll..Not too much SED interest on this item ... :( Too homeworkish I suppose..
I figured it out (or I'm very close)...and it took me all freakn day :( Only uses 1 schmitt NAND gates, 1 resistor and 1 capacitor.
One NAND schmitt gate is configured as a hysteretic oscillator. The control signal G connects to one of that gate inputs. The result is inverted but that's easy to fix. I'm checking it out with spice.
By the way... I goofed with the classic osc schematic..forgot one R
+-=NAND---+-=NAND--+ | R C +----R----+--------+Also note...this circuit may not oscillate. 3 gates are needed for assured oscillation.
I used neither config.. Instead, used a single gate oscillator.
D from BC
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