以OTRA及電阻器而不使用電容器所設計之三階振盪電路

運算轉阻放大器(Operational Trans-Resistance Amplifier；OTRA)，其關係式為，特性與運算轉導放大器(Operational Trans-Conductance Amplifier；OTA)對偶，OTA為廣泛使用之元件，因此OTRA在電路設計有著先天上的優勢。許多以OTRA為主動元件之電路設計，假設Rm值趨近無限大，然而Rm並非無限大，所以造成較大之誤差。而本文假設Rm為有限值，當操作頻率遠大於主極點時，可得轉移等效電容。此方法Rm較接近實際情形並以等效轉移電容取代實際電容，達成無電容之振盪器。本文使用導納矩陣分析設計法，完成矩陣後，將矩陣分解成三個方程式，再以基本架構組成完整電路，基本架構為OTRA的正負輸入端和輸入電壓間連接電阻，且有以下三種特性，1.每個方程式需包含一個由OTRA實現的轉移等效電容2.方程式中除轉移電容為正的一項外，將其他各項移往方程式的另一邊，正項表示信號從OTRA的正端輸入3.方程式中除轉移電容為正的一項外，將其他各項移往方程式的另一邊，負項表示信號從OTRA的負端輸入，完成後的電路為三階振盪器，由三顆OTRA以及五顆電阻所組成。模擬使用HSPICE 軟體，及TSMC035μm 製程參數進行模擬。電路模擬結果與原先設計接近。最後，調降OTRA的偏壓Vbias，及變動OTRA中的電晶體長度L，來控制振盪器之振幅。

關鍵字

無電容；振盪器；運算轉阻放大器

並列摘要

Operational Trans-Resistance Amplifier(OTRA) can be described by the equation . OTRA is dual to Operational Trans-Conductance Amplifier (OTA) which is extensively used in analog circuit design . For this reason , OTRA has great potential in the future. In the past, designer used to let the (transresistance gain) of OTRA approach to infinity ,but in real circuit it's not accurate , is finite. Actually,OTRA can be approximated as a transfer capacitor. By this method, it's not need any capacitors in circuit. According to admittance matrix analytical synthesis method, we completed matrix and decomposed it into three equations. Each equation can be achieved by basic circuit structure and has four features: 1. Each equation must include a transfer equivalent capacitance of OTRA. 2.Items are in another side of equation except the positive equivalent capacitance of OTRA .Positive items mean input signals from OTRA‘s positive side. 3.Negative items mean input signals from OTRA‘s negative side. This thesis proposed a third-order oscillator using OTRAs and resistors without capacitors. The circuit simulated with TSMC035μm process by HSPICE. The simulation result is closed to our design. Finally, we controlled the amplitude of oscillator by changing length(L) of MOS and V¬bias of OTRA.

並列關鍵字

Oscillator ； OTRA

參考文獻

[1] C. M. Chang and B. M. Al-Hashimi, “Analytical synthesis of voltagemode OTA-C all-pass filters for high frequency operation,” in Proc.IEEE Int. Symp. Circuits Syst. (ISCAS) , vol. I, pp. 461–464, May. 2003.

[3] C. M. Chang, B. M. Al-Hashimi, Y. Sun, and J. N. Ross, “New highorder filter structures using single-ended-inp ut OTAs and grounded capacitors,”IEEE Trans. Circuits Syst. II, Exp. Briefs, vol. 51, no. 9, pp.458–463, Sep. 2004.

[4] C. M. Chang, C. L. Hou, W. Y. Chung, J. W. Horng, and C. K. Tu, “Analytical

[5] C. M. Chang, “Analytical synthesis of the digitally programmable voltage-mode OTA-C universal biquad,” IEEE Trans. Circuits Syst. II,Exp. Briefs, vol. 53, no. 8, pp. 407–411, Aug. 2006.

[6] K. C. Smith and A. Sedra, ―The current conveyor-a new circuit building block‖,

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以OTRA及電阻器而不使用電容器所設計之三階振盪電路

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