A feedback control technique to compensate for the temperature dependence of the transconductance of CMOS transistors and its application in g(m)-C filters

Transconductance-C (gm-C) filters are suitable solutions to perform a variety of signal processing tasks. Operational Transconductance Amplifiers (OTAs) are main components of gm-C filters, and variable transconductance gain (gm) has a detrimental effect on the performance of gm-C filters. One principal factor to cause such variations of the transconductance (gm) values is the change in environment temperature. In this thesis, a new negative feedback technique is applied to stabilize changes in the transconductance of CMOS OTA with temperature variation over the industrial temperature range of -30°C to +85°C. Stabilized transconductance will bring stability in the frequency and quality factor of the filters built from these OTAs. To validate this notion, several types of second-order gm-C filters have been built with the temperature stabilized OTAs. Furthermore, a second-order gm-C band-pass filter with the negative feedback control system has been implemented using TSMC 0.18 mum CMOS technology, and fabricated through the facilities of Canadian Microelectronics Corporation (CMC). The experimental results show good agreement with the theoretical expectation.