So if using the RC circuit time constant, and just duty cycle calculations, these types of circuits can be solved, since the well working op-amp's take care of the details.From a TI CD4093 datasheet:
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If you don't want a control input, you can tie the two inputs together or use a single inverter from a CD40106. You may need to buffer the output in some cases.
A CMOS Schmitt inverter only takes 6 MOSFETs. I haven't tried making one from discrete MOSFETs, but have used the MOSFETs in a CD4007 to make one. May try making one with discrete devices now that I have some complementary MOSFETs.So you don't have to do any crazy transistor models
by Jake Hertz
by Don Wilcher
by Duane Benson
by Jake Hertz