Pulse wave with no DC

[jorgen.bergfors at idg.se]

Hi synthesists.

Yesterday evening I tested a little circuit that cancels the DC component that you get when you modulate the pulse width on a VCO. Roman Sowa came up with the excellent idea to just add the CV to the output.

I added an extra op-amp after the comparator that generates the pulse wave. A 62k resistor goes from the comparator output to the inverting input. A 22k feedback resistor from output to inveriing input
A 22k resistor from non-inverting input to ground.
A 22k resistor from PW CV to inverting input. A 1k resistor from output to output jack, as usual.

Now the wave will be automatically shifted to cancel the DC. You also have the added bonus that the signal level vill be reduced to 10V p-p without passive voltage divider.

A gotcha with this circuit is that you can't use 4066/4051 for waveform selection anymore. This is because the peaks now can go between -10 and + 10 volts.

Happy soldering
/Jorgen