| This thesis presents the design of a 0.5 V rail-to-rail input operational transconductance amplifier (OTA) and its application in low-frequency continuous time filters. The OTA was designed in a 0.18 mum, 0.45 V V T CMOS process. Rail-to-rail input and operation at a 0.5 V supply voltage are made possibly by using the transistor's bulk terminal as the input. An improved bulk-input common-mode feedback (CMFB) circuit has been designed which does not load the OTA compared to prior art. A self-cascode load structure and partial positive feedback provide higher gain. The bulk terminals of all transistors have been biased to lower their threshold voltages (VT) and maximize signal swing. The OTA operates at a supply voltage of 0.5 V and consumes only 28 muW of power. For a load of 20 pF the OTA has a measured DC gain of 63 dB and a gain-bandwidth product of 570 kHz. These specifications make the OTA ideally suited for low power sensor applications. To demonstrate the use of the OTA in practical circuits, three active RC filters were designed: a 10 kHz Butterworth filter, a 10 kHz Bessel filter, and a 2.5 kHz Tschebycheff filter. |
