電流式主動元件在類比電路上之設計與研究

The Design And Reasearch Of Current- Mode Active Elements For Analog Circuits

蔡尚義(Shang-Yih Tsai)

指導教授 ： 侯俊禮 ； 洪君維

中原大學/工學院/電子工程研究所/碩士(2006年)

https://doi.org/10.6840/cycu200600159

摘要

本論文提出了三個新穎的類比電路。文中所提出的第一個電路是使用一個正型第一代電流傳輸器(Plus Type First Generation Current Conveyor, CCI+)、一個接地電阻器、一個浮接電阻器及兩個接地電容器所組成的電流式正交振盪器。所提出的電路提供以下優點:(1)使用接地電容器,適合於IC化的製作; (2)振盪頻率(ω0)不受CCI+的電壓與電流追隨誤差的影響; (3)振盪頻率(ω0)對被動元件(R or C)有低靈敏度; (4)可獲得輸出電流是兩個相位差90度的弦波信號。所提出的電路使用TSMC 0.35um製程參數,Hspice模擬軟體做驗證。從模擬的結果顯示,此電路確實可得到兩個正交弦波電流信號,其相位差為90.702度,振盪頻率為16KHz。電路可振盪的頻率範圍為16.2~162KHz之間。
本文所提出的第二個電路是使用一個電流運算放大器(Current Operational Amplifier, COA)、兩個接地電阻、一個虛接地電阻所組成的史密特觸發器。此電路有別於一般傳統的史密特觸發器電路,是以電流為形式做信號處理。電路經Hspice軟體驗證其具有史密特觸發器性質。然而,電路在實際製作成IC時,因受到製程參數飄移而造成電路的臨界電流值改變。因此作者提出一改進電路,將先前電路中的一個接地電阻以兩個二極體與兩個OTA接地電阻取代,使臨界電流值可利用OTA內部偏壓來獨立調整。非常實用與方便。為了驗證此項優點,作者亦使用TSMC 0.35um 製程環境做電路模擬。由模擬結果顯示,電路確實可利用OTA內部偏壓值來改變電路轉移特性曲線中的臨界電流值。此外,作者亦在文中比較從模擬結果與理論分析所得到的正負臨界電流值,並於文中討論此兩者產生誤差的主因。
本文所提出的第三個電路是使用兩個電流差分緩衝放大器(Current Differencing Buffered Amplifiers, CDBAs)、六個導納元件所組成的單輸入雙輸出二階電壓式濾波器架構。此濾波架構藉由適當地選擇導納元件,可實現許多種類型的電壓式多功能濾波器。在本文中,兩個可實現的多功能濾波電路已被分析與討論,其提供以下幾項優點:(1)使用接地或虛接地被動元件,因此濾波電路免受寄生電容效應,且適合於高頻操作; (2)輸出端為低輸出電阻,適合於下一級的串接; (3)主動與被動靈敏度均小於一; (4)ω0與Q可以獨立調整; (5)兩種多功能濾波電路,可實現六種濾波功能; (6)使用到所有的CDBA端點。為了驗證此多功能濾波電路,作者使用Hspice軟體模擬文中所討論到的濾波電路。由模擬結果顯示,電路均符合理論分析與預估。

關鍵字

電壓式濾波器 ； 史密特觸發器 ； 運算轉導放大器 ； 第一代電流傳輸器 ； 正交振盪器 ； 電流差分緩衝放大器 ； 電流運算放大器

並列摘要

In this thesis, three novel analog circuits are presented. The first proposed circuit is a current-mode quadrature oscillator which employs one plus-type first generation current conveyor (CCI+), two grounded resistors, one floating resistor and two grounded capacitors. The proposed circuit offers the following advantages:(1) uses the grounded capacitors, which are suitable for IC realizations; (2) has no effect on the voltage and current tracking errors of CCI+ to the oscillation frequency(ω0); (3) has low sensitivities of oscillation frequency (ω0) to the passive components(R or C); (4) obtains two output current-mode sinusoidal waveforms with 90 degrees phase difference. The proposed circuit has been verified by Hspice simulation software in TSMC 0.35um process parameters. From the simulation results, the circuit can exactly obtain two quadrature sinusoidal current signals with 90.702 degrees phase difference and 16KHz oscillation frequencies. The available range of oscillation frequency for this circuit is from 16.2KHz to 162KHz.
The second proposed circuit in this thesis is a Schmitt Trigger employing a Current Operational Amplifier, two grounded resistors and one virtually-grounded resistor. This Schmitt Trigger circuit is different from the traditional ones because it processes signals in current mode ways. The proposed circuit has been verified by Hspice software which owns the property of Schmitt Trigger. However, when it is fabricated in IC, the threshold currents of this circuit will change due to the drift of process parameters. Therefore, the author proposed an improved circuit, which replaces one grounded resistor in the previous circuit with two diodes and two OTA-connected grounded resistors. This modification makes the threshold currents can be independently adjustable by the internal bias voltages of OTA-connected grounded resistors. It’s practical and convenient. In order to verify this advantage, the author also simulated the improved circuit in the environment of TSMC 0.35um Techonology. From the simulation results, the threshold currents in transfer characteristic curve can be changed exactly by the internal bias voltages of OTAs in this circuit. Besides, the author also compares the values of threshold currents with the simulation results and the theoretical analysis and discusses the main cause of errors between them.
The third proposed circuit in this thesis is a single input dual output voltage mode biquadratic filter topology using two current differencing buffered amplifiers and six admittance elements. The proposed topology can realize many types of voltage mode multifunction filters by properly choosing the admittances. In this work, two realizable multifunction filter circuits have been analyzed and discussed, which offer the following advantages: (1) employ grounded or virtually grounded passive elements, thus the filter circuits are free from the stray capacitance effect and suitable for high frequency operation; (2) have low output resistance terminals, which are cascadable to the next stage; (3) have low active and passive sensitivities, which are all less than unity; (4) tune ω0 and Q independently; (5) realize six filter responses in two multifunction filters; (6) use all the terminals of CDBAs. In order to verify the multifunction circuits, the author used Hspice software to simulate each different architectures filter circuits. From the simulation results, the circuits all agreed well with the theoretical analysis and predictions.

並列關鍵字

Current Differencing Buffered Amplifier ； First Generation Current Conveyor ； Voltage Mode Filter ； Operational Transconductance Amplifier ； Schmitt Trigger ； Current Operational Amplifier ； Quadrature Oscillator

參考文獻

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[3] G. W. Roberts and A. S. Sedra, ”All current-mode frequency selective circuits,” IEE Electronics Letters,vol.25,No.12,1989,pp.759~761.

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