High frequency model of transistor

 We discussed small signal analysis of BJT  under the key word "Small signal analysis". When input signal to an amplifier is in the range of ten to hundred  Kilo Hertz, a small signal-low frequency model of the transistor can be used for analysis. But as the frequency increases, internal capacitance of the transistor will strongly effect it's performance. A low frequency model cannot work well in this situation. To accommodate these performance changes of the transistor, a separate model  is developed for high frequency operations. This high frequency model is given in Fig 1. A high frequency hybrid-pi model is  also known as Giacoletto model.

Integrator & Differentiator-B Tech university Question & answer

Q1. Explain the working of RC low pass filter, how it can be act as an integrator.

  Answer key: circuit(2), working+fre response(4), act as integrator(5), output(1)                          (12 marks)

 To know, how to prepare answer key, visit link.
 Answer:
Consider a first order RC circuit. It can be act as a low pass filter and allows to pass only the low frequency signals.

Small Signal - Low frequency - Analysis of common collector amplifier-continue

Analysis of amplifier circuit includes derivation of equation for 1)input resistance 2)output resistance 3)voltage gain and 4)current gain. Derivation and analysis of input resistance is given in - 'Analysis of Common Collector amplifier (Emitter Follower) -begins here' . Remaining parameters will be discussed here.

Before beginning, recollect the common collector amplifier circuit and it's small signal model. It was discussed in detail in the -'begins here' post. For your convenience once again giving the circuits.
Here is the amplifier circuit:

fig 1

Small Signal-Low frequency- Analysis of Common Collector amplifier (Emitter Follower) -begins here

We are very familiar with common collector circuits- otherwise known as Emitter follower. Collector terminal is common to both input side and output side. During analysis, we are finding out the nature(characteristics) of the circuit by observing it's input and output resistances, voltage gain and current gain. Here discussing the analysis of CC amplifier using low frequency - small amplitude signals.