Design of CMOS based Programmable Gain Operational Amplifier

Variable Gain Amplifier (VGA) is an integral part of Analog Systems, a special class of VGA called the Programmable Variable Gain Amplifier (PVGA) has revolutionized modern electronic systems. In this paper a highly specific Programmable Gain Operational Amplifier (PGOA) is presented. The Op-Amp design is based on a low distortion source coupled differential amplifier model. The gain of the Op-Amp is varied by adjusting an array of internal series and feedback resistors; to facilitate this setting, three 8-bit programmable registers are provided using which a gain of 24 dB can be attained. Additionally, the design also features two 8-bit registers for status read back operation of the Op-Amp. The overall gain of the Op-Amp varies from -12dB to 12dB for a single stage. The design is embedded application interface compatible. The PGOA is an ideal solution to systems which require variable gain in real time applications and in signal processing. The modeling of the PGOA is made using CMOS device technology and the detailed analysis is summarized.