30-100 MHz npn-only variable-gain class AB companding-based filters for 1.2 V applications

Abstract

Companding can be used to maintain reasonable dynamic range (DR) in integrated analog signal processors where the allowable voltage swings are limited by the low-voltage supply requirements of modern low-power applications. The input signal is compressed before being processed, which ensures signal integrity over a large range of signal levels. At the output, the signal is expanded to restore its dynamic range. This results in a higher output signal-to-noise ratio (SNR) compared to conventional analog signal processors. Unlike the latter, the higher SNR does not come at the expense of increased power dissipation or chip area for a given bandwidth. The dynamic range of low-voltage companding analog circuits can be significantly extended using class AB current mode based signal processors.