UNIVERSAL CONSTANT-G(M) INPUT-STAGE ARCHITECTURES FOR LOW-VOLTAGE OP AMPS

In this paper, a novel design technique for low-voltage, constant tran sconductance (g(m)) Op Amp input stages is presented, The new techniqu e which uses current-mode circuits is based on processing signal curre nts, rather than handling de tail currents, to achieve a constant-g(m) . Two cases are developed, One is based on processing signal currents( the ac case) while the other is based on processing total instantaneou s currents (the TIC case), The adopted design strategy in both cases i s universal in that it is independent of the input stage transistor ty pes (FET or Bipolar) and their operating regions, It also considerably simplifies the design procedure of low-voltage Op Amps, To demonstrat e the new concepts, universal Op Amp input stage architectures have be en developed and their performances have been verified in both MOS and Bipolar design examples, The MOS designs have been verified in both w eak and strong inversion, The proposed universal implementations achie ve almost constant-g(m), independent of the common mode input voltage range from rail-to-rail.