Ring Oscillator

[theCheetah]

Why is it that they quote ring oscillator delay, whicle talking about logic gates and process. Why a ring oscillator delay, why not an individual gate delay. What is the significance of a ring oscillator! 😕

 

[highwire]

OK, I'll show my ignorance. What devices are spec'd with ring oscillator gate delay?

BTW, the ring oscillator scheme is to hook a short string of gates from the output back to the input such that the logic states are inconsistent. It will then oscillate at a frequency dependent on gate delay. However, the wave forms may not go to complete logic states, so the delays determined by this method may be a bit optimistic - I'm guessing.

I used this with RCA cmos gates more than a while ago, since a pulse generator is not needed. Didn't know I was on the cutting edge. 😀
Anyway, it is a very convenient way to compare gate delays.

 

[rimshaker]

Think of it as just a standard benchmark to quickly identify propagation delay and speed. Individual gate delay is of no help because in any finished product, all gates are interconnected, and each might have its own parasitic characteristics that effect the overall signal at the output. Just to review, the gates are simple inverters (2 transistors each), and are always performed using an odd number of total gates.