Author Topic: Understanding this circuit  (Read 712 times)

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Offline Red_MicroTopic starter

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Understanding this circuit
« on: February 16, 2020, 03:00:18 am »
Hi,

I can't wrap my head around the circuit attached. U2 comparator is acting as multivibrator, right? It's weird that U2 is powered from GND and -12V.  All I know about this circuit is that it is used to inject an AC signal to the test coil when PB1 is pressed. But how does it exactly work?
 

Offline graybeard

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Re: Understanding this circuit
« Reply #1 on: February 16, 2020, 03:43:04 am »
Yes it is a relaxation oscillator turning the fet it is driving on and off.  Ground is arbitrary, it can be any rail. 
I recently designed a circuit where I ran my 5V logic from GND on the high side to -5V on the low side because it made sense for the rest of the circuit.

The switch turns on M1 and its load.  M1 is shut off when M2 is on.


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