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In CircuitLab simulations, a [ring oscillator] (https://www.circuitlab.com/editor/#?id=uhd6a3) and a [JK flip flop with high inputs] (https://www.circuitlab.com/editor/#?id=t46rmz) both work fine with "digital" inverters and NAND gates, respectively. But they don't work when the gates are built with FETs in standard CMOS architecture. See [FET ring oscillator] (https://www.circuitlab.com/editor/#?id=9qbz48) and [FET JK oscillator] (https://www.circuitlab.com/editor/#?id=txp6pv).

I'd appreciate some advice on what the problem is. Thanks.

I'm new at this, so I'm not sure if my link formatting will work. I didn't understand how much of the URL to include for a screen shot.

It looks like I could also use some advice on formatting links.

We'll see if this works any better.

Here's my question again, edited for clarity, I hope.

Simple, standard oscillators don't seem to work as advertised if they are built from scratch.

In CircuitLab simulations, a ring oscillator and a JK flip flop with high inputs both work fine if they are composed of "digital" inverters and NAND gates, respectively. But they don't work when the gates are built with FETs using standard CMOS architecture.

I'd appreciate some advice on what the problem is.

Thanks.

I solved the ring oscillator problem with a little asymmetry - a 5 ns boost in Vdd to one of the inverters.

@ldyoder,

Good call.

I'd tried using this expression to ramp up the 5V supply:

5*(1-exp(-T/1n))

but that hadn't worked so I was having another think about it.

I hadn't thought of kicking only one stage!

Sounds like you've got the hang of kicking the supply rail but these might be worth looking at for info:

https://www.circuitlab.com/circuit/b24363/ramped-and-glitched-signals-and-supplies-01/

:)

@signality,

Thanks!

I still haven't been able to get a JK oscillator to work.

@Idyoder, could you post the circuit which includes the boost that allowed you to get the ring oscillator to work? I've been trying to get it work for a while now with no success

see Vdd_init here: https://www.circuitlab.com/editor/#?id=bye5ea