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.

Small Signal - Low frequency - Analysis of Common Base amplifier using hybrid model

 Small Signal - Low frequency - Analysis of Common Base amplifier.. Yes, the characteristics of a CB amplifier is analyzing using low frequency -small amplitude signal. Analysis of CE amplifier is in another post. Better to go through it before diving into this.

 As discussed in previous posts, analysis requires three steps - 1)Taking the circuit which is to be analyzed 2)obtaining the small signal model and 3)finding out equations for parameters helps to get approximate values and it in turn will help to predict the characteristics of the circuit.

Small Signal - Low frequency - Analysis of CE amplifier using hybrid π model

 Here we are stepping to a zone mostly liked by questioners for essay - Low frequency analysis of CE amplifier . Small signal analysis of common emitter amplifier can be done using hybrid π model. Here low frequency analysis is considered.

In order to do the analysis of certain circuit, first step is to draw the model of that circuit. This model will help us to easily find equations for certain parameters of the circuit. Usually, input and output resistances, voltage gain and current gain are these four parameters. The equations will give an idea about the approximate value of these parameters and this in turn will help us to comment about characteristics of the circuit.  

Let's start...

Transistor analysis - Small signal analysis and Large signal analysis

We can divide analysis of diode and transistor into Small signal analysis and Large signal analysis.

Large signal analysis

While doing a large signal analysis, a large dc voltage is applied and find out the behavior of diode or transistor towards this signal(find an operating point of these components). The voltage applied are of the order of few volts to few tens of volts. Here we use current and voltage equations such as 

to find bias points. This analysis is applicable to any value of current and voltage applied to the devices.

Small signal analysis

Small signal analysis approximate nonlinear behavior of  electronic components with linear equations. This approximation is taken across the bias point.