Tunable OA, tunable OTA-grounded CLow-pass, Band-pass and Band-reject Filter Structure

• Main Authors: Chih-Ting Wu, 吳誌庭
• Other Authors: Chun-Ming Chang
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/46328316415999909782

碩士 === 中原大學 === 電機工程研究所 === 94 === 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 Ao is the gain, ω0 the bandwidth, and Bo 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 Bo variable, like the transconductance of an OTA, or not? In this thesis, we have found that the Bo 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. In this paper, the proposed a realization of voltage-mode and transresistance-mode filter using devices such as tunable OTA, tunable OA, leading to very precise output responses such as lowpass, bandpass, and band-reject filtering signals. In this paper, we discuss the parasiticts effects of OAs and OTAs on the circuit characteristics. Considering the non-idealities of the OAs and OTAs, the open-loop gain A(s) and the transconductance gain G(s) are assumed to be of the following forms: , . Finally, the H-spice simulation with TSMC035 process verifies the theoretical predictions.