[SOLVED] Advantage of having linearity in output?

[Barca09]

for common source amplifiers, we make the output linearly dependent with the input by reducing the gain(source degeneration)... so what are the advantages of having this linearity in the circuit? also, doesn't this increase the undesired body effect?

 

[crutschow]

Normally you want a linear amplifier to be ideally linear with no distortion from input to output. If you don't care about distortion of the signal than you don't need to worry about the amplifier linearity. For example you are likely less concerned about distortion in RF amps as compared to audio amps.

Source degeneration may increase the body effect but the overall effect is still an increase in linearity.

 

[LvW]

for common source amplifiers, we make the output linearly dependent with the input by reducing the gain(source degeneration)... so what are the advantages of having this linearity in the circuit? also, doesn't this increase the undesired body effect?

Do you know what a non-linear input-output characteristic does with a sinusoidal wave at the input?

 

[Barca09]

Do you know what a non-linear input-output characteristic does with a sinusoidal wave at the input?

The resulting sinusoid will have a frequency other than the original frequency 'f' ?

 

[LvW]

The resulting sinusoid will have a frequency other than the original frequency 'f' ?

Not quite correct. It will be no sinus anymore. That means: The output will be something we call "distorted sinus" (depending on the kind of non-linearity it will look more or less like a squarewave or like a triangle or something in between). Applying a FOURIER analysis to this output signal will reveal a fundamental (sinusoidal) component of the original frequency together with harmonics (multiples of this fundamental). The "quality" of this output if compared with the clean input can be expressed by a factor called "total harmonic distortion (THD)" given in %.

 

[varunkant2k]

doesn't this increase the undesired body effect?

What is meaning by undesired effect?
What does Body effect do? It reduces the source resistance (1/(gm +gmb)) and increases the threshold voltage. As long as you are having good gain and supply overhead, you may not be worried by body effect.
Advantage of linearity for output stage MOSFET is that, if it is linear, it is less dependent on process/temperature related gain parameters. ouput stage gain will be constant over the operating range.