Pseudo-differential OTA Design with ±0.9V Wide Input Swing Range in 0.18μm Submicron Technology

In this paper we present a novel approach in the design of a pseudo-differential operational transconductance amplifier having a wide input range being adapted to the implementation of a 9th-order Bessel filter. Inclusion of a PMOS device biased at the subthreshold and triode regions facilitated an improvement of 40% in the input swing range by suspending half of the supply, while maintaining degradation of transconductance Gm to less than 1%. The operational transconductance amplifier is fabricated using a 0.18-µm n-well 1P5M CMOS process with a 1.8V supply. Results through measurement show 1% Gm variation, and a total harmonic distortion of below −62dB under the input swing range of ±0.9V. The 9th order Bessel filter shows the cutoff frequency of 100MHz highly desirable for a digital versatile disc pickup circuit operating at 16 times normal speed.