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Why small signal analysis?

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harivadakara

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What is small signal analysis and why it is important?
What is the difference between small signal and large signal? pls help:)
 

Dear harivadakara
Hi
The small signal analysis of amplifiers , is important , because the amplifiers at large signal are logarithmic and thus , the equations are a bit complicated .
And i think another reason , is that we can solve our problems , simply with this kind of analysis .
Best Wishes
Goldsmith
 

Looking at an amplifier characteristics curve it is a non-linear circuit in general and analysing a non-linear circuit is a bit difficult. In order to simplify the analysis we impose a condition on the input signal that it should be small relative to the linear region of the characteristics curve and treat the amplifier as a linear circuit. The linearity implies that it holds the superposition and homogeneity principles and thus we can find first the DC and then the AC response of the circuit and can get the total behaviour of the amplifier. I hope it may Help...
 
Large signal analysis allows you find the DC operating point of a circuit. Small signal analysis allows you to find the result of applying a small (AC) signal on top of the DC operating points of a circuit. For example, in an 1-transistor NMOS amplifier, you need to first find the Idrain-source current with the applied Vgate and Vdrain-source voltages. This is your "large signal analysis". Then you need to see what happens when a small AC signal is applied at the gate of the transistor (i.e. how much Ids current is produced when I apply my small AC signal). Remember that small signal analysis assumes linearity (i.e. the change in your small AC signal is much smaller relative to the DC operating point). :-D
 

Large signal analysis is also needed for all switching and digital simulations. AC analysis only works with linear circuits and sinewaves.
 

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