Multivibrators: IC vs. Discrete versions

Hey there!

I did learned many basic and intricate workings of Multivibrators inside the IC555 timer in my college - they are okay and quite understandable because of the R-S flip-flop thingy (I build a truth table for this) and the pair of comparators.

Unfortunately, the discrete versions AIN'T easy. The last part - Astable using 2 BJTs are horribly difficult to be understood. I know there's positive feedback inside these configurations, like the ones in Op-amps, but the discrete versions just made my head spin.

To be honest, I can build up all three types of multivibrators using IC555 myself with the aid of my knowledge, but NOT any of these discrete versions.

Anyone has experience learning the discrete versions of these Multivibrators in college?

Discrete multi-vibrators are really simple to understand, and I wouldn't class a 555 as a multivibrator at all.

In order to understand one, remove the capacitors (leaving two transistors and four resistors) and see if you can understand how that works?.

Nigel Goodwin said:

Discrete multi-vibrators are really simple to understand, and I wouldn't class a 555 as a multivibrator at all.

In order to understand one, remove the capacitors (leaving two transistors and four resistors) and see if you can understand how that works?.

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I see. Now, in college, the 555 versions of these multivibrators are in my course syllabus. So I have to read 'em up and understand 'em.

Just to satisfy my curiosity, I wonder what's these multivibrators before 1971? That must be the discrete versions anyway I guess. Maybe in my free time I'll think about the discrete ones.

https://en.wikipedia.org/wiki/Multivibrator

Going further back they used valves and before valves relays were used.