As you say, it does depend on your transistor's gain, somewhat, but those are all over the place, even in a single batch. The original Serge design used a 47k instead of a 150k there. Personally, I prefer to use voltage followers in this sort of location, as they give a more gradual LED response. You could try a higher base resistor if you wish.
On Wed, May 18, 2016 at 1:49 AM, guymccusker@... [cgs_synth] <cgs_synth@yahoogroups.com> wrote:Thanks very much Ken. I will experiment a bit.
I'm surprised to hear that the driver circuit won't need adjustment. To take the example of a 10k resistor on the LED, with a 12V supply this will saturate at about 1mA (10V drop across the resistor). Assuming hFE of about 100, that means a driving current of 0.01mA to fully switch the LED on, which means a .5V drop across the base resistor, so the LED fully lights when the output hits just over 1V.I am new at this so my calculations could be completely wrong! I will fiddle about and see what I come up with.Is the idea to have the LED pulse along with the DC output, so that with a slow cycle you would see the light go from off to soft to bright and back? And, for experimental purposes, is the output supposed to be 0 - 5V?Thanks again for any help you can offer.
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