My question is, does C(E) and r(E)(not showed) at Q1 have effect on the lower or upper -3dB frequency? I think there is, depending on the value of the C(E). Am I correct? But the solution give for this question is: Lower -3dB: decide by : R(L1)//H(oe)+R3//R4 and C(c) Upper -3dB: decide by: R(L1)//H(oe)//R3//R4 and C(s)
Perhaps you are meant to assume CE is sufficiently large that it doesn't impact the -3dB cut-off point and plays a role well below the initial -3dB frequency transition.
So do you mean I am correct in theory, but the question here want me to assume C(E) is large enough. Practically, in most situations, would C(E) play a role in the -3dB cut-off point, or usually not the case. Or it really depends on the specify circuit?
Yes that's what I mean. It depends on the relative time constants for the emitter and collector topologies. If one sees [say] 50Ω looking back into Q1 emitter terminal then what value of CE would ensure the emitter time constant is an order of magnitude greater that the derived collector time constant?
