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jason9
modified 6 years ago

Inverting Schmitt Trigger Oscillator

2
7
115
02:45:19
I tuned it to have an equal rise and fall time.
published 7 years ago
Issacsutt
7 years ago
Jason9, I've tried and tried to understand oscillators myself, trying to come up with my own designs... but nothing works right. It appears like you know what your doing, and understand how to manipulate feedback -which I think I see you've done through a resistor voltage divider, and I believe mastering feedback may be the root of my problems here. Anyway, please enlighten me on this, and explain this how you understand it if you can... I would really appreciate it!
jason9
7 years ago
Ok, the basis of most oscillators is a frequency dependent feedback that phase shifts the signal by 180 degrees only at a specific frequency. Then, an inverting amplifier amplifies it and phase shifts it at another 180 degrees, for a full 360 degree phase shift. Then, in order for it to sustain amplify oscillations, the amplifier has to have sufficient gain such that the oscillations won't die out. The frequency is determined by the frequency that the initial phase shift shifts the phase by 180 degrees. Generally, the initial phase shift is done by an RC or LC network. This oscillator is a little unique, as it's an inverting Schmitt trigger oscillator. The way a Schmitt trigger works is that if the input passes a certain threshold, say 8V, then the Schmitt trigger's output goes high. Then, the input has to pass 4V for it to revert back to outputting low. An inverting Schmitt trigger works the same way, just that the output goes high when the input goes sufficiently low, and visa versa. That way, the output simply has to be fed back to the input and it's an oscillator.
jason9
7 years ago
See my latest circuit.
Issacsutt
7 years ago
Oh ok, hurz tried explaining it too before, but he never mentioned that it could only oscillate at a specific frequency
Issacsutt
7 years ago
So then, if I want to use rc circuits only to control the timing, how do you figure out what frequency it'll oscillate at, and how much gain you need?
jason9
7 years ago
Look at my most recent circuit to find out how I usually do it.
Issacsutt
7 years ago
You really like to use inductors for some reason?!? :)

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