| Summary: | 碩士 === 中原大學 === 電機工程研究所 === 94 === Abstract
It is worthy of research to do the analogue circuit design using Operational Transconductance Amplifiers (OTAs) and Capacitors (Cs) because an OTA is equivalent to both an active element and a resistor leading to a more condensed integrated circuit without resistors, and because the equivalent resistor value can be electronically tuned varying the bias current.
Due to the difficulty to precisely fabricate the capacitance in integrated circuits, it becomes an important research work to find a tunable element for the replacement of the capacitor used to realize the s terms in transfer functions. The input-and-output relationship of an Operational Amplifier (OA) is shown as below.
in which A0 is the gain, ω0 the bandwidth, and B0 the product of both gain and bandwidth. It is exhibited that an OA can also be used to realize the s terms in transfer functions.
Hence, is the B0 variable, as the transconductance of an OTA, or not? In this thesis, we have found that the B0 is variable tuning either the bias current or the inner compensation capacitance of an OA just like the variation of the transconductance of an OTA through the tuning of its bias current. Therefore, the capacitor with error fabricated in the integrated circuits can be replaced by the OA tunable through its inner bias current.
The thesis is focused on the design of biquads using both tunable OA and tunable OTA, leading to very precise output responses such as lowpass, bandpass, and band-reject filtering signals. Finally, the H-spice simulation with TSMC035 process verifies the theoretical predictions.
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