I wonder what the purpose of the coupling capacitors and the bypass capacitors are and the type of effect each capacitor has on the circuit.
As I've understood it, you use coupling capacitors to block DC and avoid interference (what does that really mean?) and the bypass capacitor is to have a short-circuit in the emitter of the transistor (and what does this really mean?).
If I vary the values of C1 and C2, what kind of effect does it have on the bandwidth of the amplified signal?
What happens if we have a large or a small bypass capacitor (C3), what effect does it have?
So in essence, what does the three capacitors do in the circuit, i.e. what low pass and high pass effect does it have?
I have an LTspice schematic that we can get a visualization from.
Best Answer
The role of C3:
It is the main purpose of C3 to restrict the negative feedback effect (caused by Re) to DC and very low frequencies (below the desired operating frequencies).
This feedback effect (for DC) is very inportant because it makes the DC operating point less sensitive to parts tolerances and variations of the transistors B-Value (B=Ic/Ib).
As another effect, negative feedback reduces the gain value - and if somebody does not want such a reduction, the feedback effect must be cancelled for operating frequencies (bypassing Re with a capacitor C3).