[SOLVED] Relation between signal swing, Dynamic range and Signal to noise ratio

[Gupsh]

Hi!
How the following 3 parametres signal swing, Dynamic range and signal too noise ratio are related. This is in relation to the fact that as we decrease the supply voltage of a circuit, it directly affects the maximum signal swing, and therefore, the dynamic range (DR) and signal to noise ratio (SNR).
Thanks !

 

[Junus2012]

Hello
I will assume that you are talking about the output swing of an operatioan amplifier with CMOS technology (the same concept for other kind amplifier)

the output swing is the maximum range where all the output transistor are still in the saturation region. this will be affected by the number of the transistors in the output stage because each one will have a voltage drop. for ideal non practical case if we ignore the voltage drop of the transistors then the output swing will be from rail to rail in the amplification region.
please dont mix between the output range of the large signal wit the small siganl output range, in the cutoff region which is not the region of the amplification, the output voltage is already at the supply rails.

the dynamic range is sometimes is referred to the output swing and some times referred to the SNR. if we do not consider the output noise then the DR is exactly the same as the output swing. if we consider the noise in the output then the DR will specify the SNR.

from my reading, it is not crucial thing to use dynamic range or the output swing.

finally the SNR give you the useful or effective output swing because it consider the noise as well. for example, having a rail to rail output swing it doesnt mean that you can use it all effectively if the noise level in the output is high

I am sorry to make it lengthy but I attached you a useful two articles

 

[Gupsh]

Thanks Junus for dropping in and answering my query

 

[Junus2012]

you are welcome