[sdiy] Op-amp to boost VC signal with +5V/GND?

[Thomas Strathmann]

On 8/23/10 17:23 , Harry Bissell wrote:
> Many classic synths use CMOS (4000 series) and 12 or 15 volt supples, which would
> require a gate voltage of between 6 to 7.5V minimum to trigger, possibly more if
> a schmitt trigger gate was used.

Tell me about it. I have build two with 4000 series Schmitt triggers on 
the front end and had to amplify the input signal quite a bit to get the 
circuits to work. In retrospect I could probably have used a discrete 
two transistor Schmitt trigger instead and done away with an additional 
gain stage.

That reminds me of a question I've wanted to ask: What's your favourite 
Schmitt trigger or way to drive CMOS ICs from a gate or trigger signal 
in modern (i.e. probably low gate voltage) synths?

> 5V is too low for a good gate imho. I think the 10V level would be best.

Yes, better save than sorry when it comes to interfaces. The little 
extra current won't hurt.

	Thomas