Supplying a DC voltage to a circuit drawing AC current

[Oreo_]

How do we analyse circuits that draw pulse currents from DC sources?

 

[Harald Kapp]

The same way we analyze any circuit:
- Kirchhoff's laws
- Norton theorem
- Thevenin theorem
- etc.

 

[HellasTechn]

I barely remember theese from school !!! to be honest i never understood any of theese lol !

what exactly can you figure out by analysing a circuit ?

 

[Harald Kapp]

How it works?

 

[HellasTechn]

You mean the mathematical details of it's function not in general how it works.

 

[Harald Kapp]

Both.
Of course, you can analyze voltages and currents in a circuit and still have no clue how it works or what it does. On the other hand you can understand what a circuit basically does, but be unable to calculate the exact behavior.
You need both: An understanding of the basic function plus the detailed analysis for exact parameters of the circuit.

Take for example the common emitter transistor amplifier in this tutorial. It is relatively easy to see that R1 and R2 set up the operating point (bias) for the transistor and that RE and RL have an influence on the collector current and that the output voltage is the AC part of the voltage drop from collector to ground.
However, to find out which values of R1, R2, RE and RL give maximum gain, you need to thoroughly calculate the circuit. Typically you replace complex components (like the transistor) by simpler models that are easier to calculate. And by takinmg into account the frequency dependent characteristic of the capacitors you can analyze how the gain of this amplifier varies with frequency.