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difference between small signal and large signal

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engrbabarmansoor

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small signal and large signal

whts the difference between small signal and large signal?
how do we know whether signal is small or large?
 

Hi,

It depends upon the signal power, for example, an ECG signal may be a candidate of small signal, BUT if you are talking about small signal analysis then its different interpretation for this.

BR,

Arif Khan
 

small signal beta

if you talking about analysis. to put it in simple way, large signal analysis is the analysis for dc analysis such current and voltage. this is essential to assure correct biasing. As for small signal analysis, it is ac analysis which required for us to know the frequency response of our circuit. Beside we do ac analysis to characterize our circuit and to find ac parameter such as phase margin and bandwith

-evilguy-
 

bjt large signal analysis

in small signal all the transistor and other nonlinear elements, work in linear region. but by increasing the signal level dependent to nonlinear element charactersitics, it works on nonlinear region.
in order to investigate on such situations we define:
IP3, IMD, ...
in power amplifire it is so important to know the large signals effects!
 

small signal and large signal difference

SMALL SIGNAL : The amplitude of the signal is small enough, so that the operation is over a very small portion of NON-LINEAR device (e.g. BJT or MOSFET) characteristic(graph). Such a small portion may be regarded as almost linear.

LARGE SIGNAL : Signal is so large that it causes the NON-LINEARITIES in the characteristic (graph) of the device to become evident.
 
ac analysis at small signal

I can provide the more clear definition for CMOS case in my experience:

real small signal: Vip < 0.25*Vov

true large signal: Vip >= Vov

Vov=Vgs-Vt

Best Regards,
Yibin.
 

difference small signal large signal

large signal

for bjt: alpha,beta
for mos: mos current equation


small signal analysis

for bjt: h parameters, gm model
for mos: gm model
 

differances large signal small signal

quite agree with evilguy's viewpoints.
 

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