# Comparators internal transistors logic explanation and examples

Hi,

Could somebody provide some basic explanation of the logic of the internal transistor circuitry of the comparators, for example an op-amp and if possible some basic examples for building comparator circuits with transistors for some home fun, for example some circuits with not more that 10 transistors? hehe thank in advance : )

Massive archive of tutorials on comparators, op amps, and more!

Jokes aside, what are you trying to do? Are you trying to build a comparator yourself out of discrete components? Do you have any specific questions about their internal circuitry?

Good idea would be to explain the work of some very basic comparator with 3 to 6 transistors circuit than some more complex circuit like an op-amp so can be understood the logic of it. Thank you!

meanwhile some notes for background hehe: https://www.youtube.com/watch?v=7QR6ytrVRkM

Well, yes, would be fun to build a comparator with 3 to 6 transistors just for the fun of it and to get more clear on the working principles of them and from this to get more clear on the op-amps having the internal circuitry of them clear. Thx

So the front end of any opamp (except extremely high speed ones) or comparator is a differential pair (aka long tailed pair). That's the circuit to play with first. and understand. A common design for any low frequency differential amplifier is differential pair as input, driving a current-mirror load. That should be enough search terms to be getting on with!

Both comparators and opamps are forms of high gain dc-coupled differential amplifier, using a differential pair input stage. However comparators are designed to be fast but not stable, and drive a logic signal (usually open collector).

Opamps are designed to be stable with large amounts of negative feedback(*), often low noise, and to drive a modest analog load in a bipolar fashion.

(*) in practice this means the gain is deliberately made to fall with increasing frequency.

Thanks for the direction fr googling. Is it possible to have also some basic schematics for direction? thx