在本篇論文中，設計了一個具有低失真性與可調整轉導值的轉導放大器，利用了電流再使用及增益推進的技巧，並把材質為金屬氧化物半導體的電晶體操作在線性區，可以得到高性度電壓與電流轉換的轉導放大器，進而使用此設計完成的轉導放大器來組成一個適用於高頻操作的轉導電容濾波器。由於轉導放大器的轉導值具有可調整性，所以利用此特性來適當地設定轉導電容濾波器的截止頻率，以用來克服晶片製程中所產生的變異。並且使用了設計在晶片上的可自動調整濾波器頻寬的迴路來決定轉導放大器的轉導值及補償製程變異的影響，此調整迴路利用了主僕式的技巧來完成設定轉導放大器的轉導值，進而達成調整濾波器的頻寬。這個迴路共包含了一個由轉導放大器所組成的積分器、兩個平方電路、一個比較器、一個數位類比轉換器和一個數位電路。

為了驗證所設計的電路，實驗晶片採用了UMC 0.18 mm CMOS製程所製作，此濾波器為一個六階的巴特渥斯低通濾波器，在電源供應為1.8 V之下，經過量測的結果，-3 dB截止頻率為5.8 MHz ~ 7.9 MHz之間，直流增益為-1 dB ~ -0.12 dB，當輸入訊號頻率是1 MHz且訊號大小為1.4 Vppd時，其THD是小於-40 dB，IIP3為11 dBV，功率消耗為11.75 mW。當啟動自動調整頻寬迴路時，濾波器的頻寬的誤差率可在5.3 %之內。

In this thesis, we <a href="http://www.ntsearch.com/search.php?q=design&v=56">design</a> an operational transconductance amplifier (OTA) with low distortion and tunable transconductance (Gm). By applying current reusing and gain boosting techniques, the MOS devices in the input stage of the proposed OTA operate in the linear region and the high linear voltage-to-current conversion can be obtained. Using this OTA, a Gm-C filter which is suitable for high frequency operation is constructed. To overcome the process variations, the transconductance of the OTA is tunable so that the cutoff frequency of the Gm-C filter can be set properly. Moreover, an on-chip automatic bandwidth tuning loop is also designed to automatically decide the transconductance of the OTA and compensate most variation effects.
To verify the designed circuits, an experimental chip is fabricated in UMC 0.18 mm CMOS process. The realized filter is a 6th-order Butterworth lowpass filter. The power supply voltage is 1.8 V. The measurement results of the filter show that the tuning range of the -3-dB bandwidth is among 5.8 MHz to 7.9 MHz and the DC gain is among –1 dB to –0.12 dB. The total harmonic distortion (THD) is small than –40 dBc when the input signal is 1 MHz sinusoidal waveform with 1.4 Vppd. The input third intercept point (IIP3) is 11 dBV, and the power consumption is 11.75 mW. When activate the on-chip automatic tuning loop, the error of the filter bandwidth is less than 5.3 %.

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