(This sort of follows on from the "Computer controlled pulse generator" topic, but it's a much narrower question that doesn't require all the previous information. The PIC quest is ongoing, but for the moment I'm taking another look at the audio idea.)
I'd like to use audio pulses to trigger a low-voltage digital circuit. (A supply voltage of 3V total, ideally.)
The original idea was an op-amp followed by some kind of transistor- and the problem was that I couldn't find anything with a low enough threshold voltage. (Even a rail-to-rail amplifier that can cope with +-1.5V doesn't quite do it. I identified a MOSFET with a 1V max threshold, but I couldn't find anywhere that sells it. And that would still be cutting it a little fine.)
(1) What would be good would be something like an op-amp that works on only one side of the zero line. I don't know what that would be called, if it exists. Single 3V supply; 0 to 3V input processable (negatives allowed and read as 0); and as near 0 to 3V output as possible (though 0.5V to 2.5V would work OK really). Is there such a thing? Or, is there some way to wire an op-amp so it'll do that?
(2) The other possibility is if there's some other kind of switch device with a threshold of less than 1V. (My brother just suggested an A/D converter chip with a parallel output, but those are pretty expensive and probably best avoided here.) Any ideas on a cheap component with that effect?
I'd like to use audio pulses to trigger a low-voltage digital circuit. (A supply voltage of 3V total, ideally.)
The original idea was an op-amp followed by some kind of transistor- and the problem was that I couldn't find anything with a low enough threshold voltage. (Even a rail-to-rail amplifier that can cope with +-1.5V doesn't quite do it. I identified a MOSFET with a 1V max threshold, but I couldn't find anywhere that sells it. And that would still be cutting it a little fine.)
(1) What would be good would be something like an op-amp that works on only one side of the zero line. I don't know what that would be called, if it exists. Single 3V supply; 0 to 3V input processable (negatives allowed and read as 0); and as near 0 to 3V output as possible (though 0.5V to 2.5V would work OK really). Is there such a thing? Or, is there some way to wire an op-amp so it'll do that?
(2) The other possibility is if there's some other kind of switch device with a threshold of less than 1V. (My brother just suggested an A/D converter chip with a parallel output, but those are pretty expensive and probably best avoided here.) Any ideas on a cheap component with that effect?