switching inputs on a 4093

schmelfhelp · Joined: Apr 15, 2012 Posts: 24 Location: france

Hi guys

I'm not sure if what I want to do is possible, or how to explain it that well but here goes.

I have two oscillators using a 4093, one of them modulates the other. I would like to make it modular within itself,

currently the first osc modulates the second one. I would like to be able to plug and unplug this connection. But when I unplug the first osc from the second I would like a high input sent to the second osc so it keeps working.

I don't want a high input permanently there as it would cancel out the input that makes it modulate.

i hope my unique way of understanding this all is understandable, thanks for any help Smile

brock · Joined: May 26, 2011 Posts: 112 Location: Canada

You need a pull-up resistor on the modulation input. 100K should be fine, you can probably go as low as 10K. Connect your positive voltage to one end of the resistor, the other connects to the input pin. When the first oscillator is plugged in it will sink more current than the pull-up resistor can provide so it can drive the pin low and high.