# Circuit analysis for the given circuit diagram

#### Priya_ece

Joined Jul 23, 2019
11
I want some help for the given circuit diagram. I want to analyze the given circuit but unable to. Also, what should be the tricks to analyze any electronic circuit no matter how complex it is?

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#### dl324

Joined Mar 30, 2015
11,317
What I'd do is eliminate the components that have nothing to do with circuit functionality (e.g the decoupling caps - they're important, but not for circuit analysis), provide values for unlabeled elements, then break the circuit into functional blocks.

Is this project school work?

#### Priya_ece

Joined Jul 23, 2019
11
Hello,

So, the SPAD is basically a reversed biased avalanche photodetector. The diodes are obvious I guess. The I1, I2, I3 are inverters. The rectangular boxes are resistors and ofcourse there is the one comparator.
Basically what this circuit is supposed to do is get the current pulse from the photodetector which further goes on to trigger the comparator's inverting terminal and set the output at high state.

I am designing a quenching operation for controlling bias voltage across my photodiode. The idea is as photons hits it, the diode produces a corresponding current pulse which I want to fed as an input of a comparator which senses the current and outputs a logic which finally triggers the biasing source i.e. when the diode is biased above breakdown, Vr while it detects the photon and gives current output then immediately the bias voltage go below the breakdown, Vc (<Vr) then again switches back to above Vr for another detection. And the process repeats at a very fast rate in order of tens of nanoseconds.

#### dl324

Joined Mar 30, 2015
11,317
You need all component values before you can do a complete analysis. It wasn't apparent to me that the diode labeled SPAD was a photodiode.

Regarding the inverters, all I can tell is that they aren't TTL.

You seem to know the function of all of the circuit blocks. At first glance, it appears to be a relatively straightforward design. What is it that you wanted help with?

Again, is this project school work? This site has special rules for school work.

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