A rail-to-rail op amp for VLSI cell with constant performance

A novel general-purpose low-voltage rail-to-rail CMOS op amp is introduced, which obtains constant transconductance, slew rate and constant high gain over the entire input common mode voltage range. The proposed scheme has the potential for the application in deep submicrometer technology, as the operation of the circuit does not exclusively rely on square-law or linear-law of transistors. The scheme is compact and suitable for the application as VLSI cell. Simulations show that in the entire range of input common mode voltage, the variation of transconductance, SR and gain are 1%, 2.3%, 1.36 dB, respectively.