1-V rail-to-rail operational amplifiers in standard CMOS technology

The constraints on the design of CMOS operational amplifiers with rail-to-r ail input range for extremely low supply voltage operation, are addressed. Two design approaches for amplifiers based on complementary input different ial pairs and a single input pair, respectively, are presented. The first r ealizes a feedforward action to accommodate the common-mode (CM) component of the input signals to the amplifier input range. The second approach perf orms a negative feedback action over the input CM signal. Two operational a mplifiers based on the proposed approaches have been designed for l-V total supply operation, and fabricated in a standard 1.2-mu m CMOS process. Expe rimental results are provided and the corresponding performances are discus sed and compared.