Nonlinear Devices for Amplitude Compression

Logarithmic compression at the input to the quantizer can improve the SNR by making it 

independent of the input signal variance. In actual implementation, where system noise defines a 

minimum signal input amplitude, this form of compression can be achieved through the use of 

log amplifiers. Likewise, by using variable gain, it is possible to adapt the signal amplitude to the 

characteristics of the quantizer. This, too, can be implemented by using automatic gain control 

(AGC) amplifiers. Both log amplifiers and AGC amplifiers are discussed in greater detail below 

[30]–[33].