A constant input transconductance and rail-to-rail input/output swing SiC CMOS op amp

A silicon carbide (SiC) CMOS op amp with a constant input transconductance and full input/output voltage swing is presented. A novel bias circuit is used to provide the bias current for both N-channel and P-channel differential pairs as a function of the input common mode voltage such that the total transconductance is virtually constant over the entire input common mode range. This scheme is also independent of transconductance parameter matching between the NMOS and PMOS transistors, thus resolving the process variation problem associated with new processes, which may be as high as 100% in the current SiC CMOS technology.