以完全差動轉導實現濾波器之研究

近幾年來，電流式主動元件受到學者和業界的愛戴，是因為電流式電路具有較大的頻寬和增益、較大的動態範圍、較精確的結果、較低的功率損耗和較小晶片面積的電路結構等優點，以證實它的優越性，也漸漸證實電流式電路比電壓式電路具有更好的精確度，由於運算轉導放大器(Operational Transconductance Amplifier, OTA)可藉由一偏壓電流改變其內部轉導值(transconductance)，因而在設計OTA-C濾波器(OTA and capacitance filter)時，無須考慮電阻接地或外加電阻的問題，本論文就是基於此種特性，提出一種新型之OTA架構，並成功的應用在雙二次式濾波器(second order biquad filter)上。本篇論文主要是以長尾對(LTP)為中心架構，並結合適應性偏壓(adaptively biased)技術產生一個適當的補償電流來補償長尾對，使輸入輸出線性範圍得以延展，設計出低電壓完全差動運算轉導放大器(low power fully differential transconductor)，從Hspice的模擬結果來看，線性範圍延展成從 -0.7V到0.7V，並將其應用在雙二次式濾波器上，可藉由一偏壓電流改變其內部轉導值，來獲得所需的角頻率(corner frequency)和品質因數(quality factor)。

關鍵字

運算轉導放大器；長尾對；適應性偏壓；濾波器；平方律

並列摘要

In recent years, the current mode active component is popular in scholastic discussion and commercial purposes. Current mode active components have the advantages of wider bandwidths, larger dynamic range, lower power consumption, smaller area and easier to design. The current-mode circuit is proved to be much more precise than its voltage-mode counter part. Since the transconductance of an operational transconductance amplifier (OTA) is electronically adjusted by the internal bias current, no resistors in the OTA-C circuit become an important advantage in the active filter design. In the thesis, the new OTA structure is presented and it is used in biquad filter. In this thesis, we proposed transconductance element with low power fully differential transconductor based on long tail differential pair (LTP) with adaptively biased technique, which generate suitable compensating current witch extend the input-output linear range. The result of Hspice simulation shows that with ±1.1V power supply, linearity range is between -0.7V and 0.7V. The proposed transconductor is used to design second order biquad filter. The transconductance of a transconductor is electronically adjusted by the internal bias current, so that suitable corner frequency and quality factor is obtained.

並列關鍵字

OTA ； LTP ； adaptively biased ； filter ； square law

參考文獻

[1] A. Nedungadi and T. R. Viswanathan, “Design of linear CMOS transconductance elements,” IEEE Trans. Circuits syst., vol. 31, pp. 891-894, 1984.

[2] A. M. Ismail and A. M. Soliman, ”Novel CMOS wide-linear-range transconductance amplifier,” IEEE Trans. Circuits syst. I, vol. 47, pp. 1248-1253, 2000.

[3] J. N. Babanezhad and G. C. Temes, “A 20-V four-quadrant CMOS analog multiplier,” IEEE J. Solid-State Circuits, vol. 11 pp. 1158-1168,1985.

[4] H. Khorramabadi, “High frequency CMOS continuous time filters,” Ph.D. dissertation, University of California, Berkeley, 1985.

[5] M. O. Shaker and S. A. Mahmoud and A. M. Soliman, “New CMOS fully differential transconductor and its application,” IEEE, Circuits and systems, 2006.

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以完全差動轉導實現濾波器之研究

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