以一階全通濾波器及積分器而不使用電容器所設計之二階振盪電路

運算轉導放大器(Operational Transconductance Amplifier)簡稱OTA，是目前用於類比電路設計中公認最佳的主動元件。另一種元件：運算轉阻放大器(Operational Trans-Resistance Amplifier)簡稱OTRA，因為與OTA有對偶的特性，是近年來電路設計學者逐漸對OTRA這個主動元件感到有興趣的原因；本論文就是以運算轉阻放大器(OTRA)當作主動元件來進行電路設計。過去，設計以OTRA為主動元件的電路時，常會假設Rm(轉阻增益值)趨近於無限大，但實際並非無限大，所以前面假設的結果產生了不可避免的輸出誤差。實際的轉阻函數Rm(s)為Rm(s)=Rmo/(1+s/wo)，當s/wo>>1時，Rm(s)=Rmo*wo/s，此時OTRA可具有等效轉移電容器的特性，除了可提高精準度，亦不需外加電容器。本論文以一階全通濾波器及積分器設計二階振盪電路，經由設計分解成多個簡單的子方程式，再由子方程式對應的子電路組合成完整電路，每個子方程式擁有以下三個特點：1.每個方程式構成之電路一定要包含一個由OTRA實現的轉移電容容納。2.方程式中除了電容容納為正的一項外，將其他各項移往方程式的另一邊，則正項表示從OTRA的正端輸入。3.方程式中除了電容容納為正的一項外，將其他各項移往方程式的另一邊，則負項表示從OTRA的負端輸入。本論文電路驗證使用H-SPICE軟體中TSMC035 m製程參數進行模擬，其結果與原先設計接近，最後藉由降低OTRA的偏壓值以及增加內部電路的電晶體長度讓輸出振幅降低，其結果符合預期。

關鍵字

振盪器；運算轉阻放大器

並列摘要

Operational Transconductance Amplifier (OTA) is considered the best component that is used in analog circuit design. Another component：Operational Trans-Resistance Amplifier (OTRA) is dual to OTA by compare OTA’s output equation with OTRA’s. In this thesis, OTRA is taken as an active component to design circuits. In the past, designer used to assume Rm (trans-resistance gain) approach to infinite. Actually, Rm is a very large value, but not infinite. Rm approach to infinite that cause an output inaccuracy. ActuallyRm(s)=Rmo/(1+s/wo), when s/wo>>1, Rm(s)=Rmo*wo/s. Now, OTRA is approximated to a transfer capacitor. It may improve the accuracy and doesn’t need real capacitors. In this thesis, second-order oscillator is proposed by using a first-order allpass filter and an integrator. Transfer function is decomposed into some sub-equations. And then we compose these sub-circuits which are come from sub-equations to complete our circuit design. There are three features of sub-equations: (1) Each equation of sub-circuit has to include an equivalent capacitance constructed from OTRA. (2) Let the capacitance be positive, besides we move other terms to another side of equation. Positive terms mean input signals from OTRA’s positive side. (3) According to previous feature, negative terms mean input signals from OTRA’s negative side. This circuit simulated with TSMC035 m process by H-SPICE, the result is close to the design. Finally, by decreasing the bias voltage of OTRA and increasing the transistor length of OTRA’s internal circuit let the output amplitude reduce. The result is the same with our expectation.

並列關鍵字

Oscillator ； OTRA

參考文獻

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[17] Chun-Li Hou, Chin-Wei Chang, Jiun-Wei Horng, “A quadrature oscillator employing the dominant poles of the OTRAs,” Journal of Advanced Engineering Vol. 2, No. 3, pp. 185-187 , July 2007.

[29] Hou, C. L., Chien, H. C., and Lo, Y. K., “Squarewave generators employing OTRAs”, IEE Proc. Circuits Devices Syst., 2005, 152, (6), pp. 718-722.

[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.

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以一階全通濾波器及積分器而不使用電容器所設計之二階振盪電路

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