※ 引述《elian1 (Baseball在面前)》之铭言： : 请问各位前辈 : junction varactor和MOS varactor比较的优缺点为何? : 我是知道个大概 但由於要写论文 所以需要详细的资料 : 但又不知道这方面的详细资料要去哪找 : 还请知道哪里找的到这些资料的前辈跟我指点一下 感激!! As supply voltages scale down, pn junctions become a less attractive choice for varactors. Specifically, two factors limit the dynamic range of pn-junction capacitances: (1) the weak dependence of the capacitance upon the reverse bias voltage, e.g., Cj = Cj0/(1+Vr/Φb)^m, where m ~ 0.3.; and (2) the narrow control voltage range if forward-biasing the varactor must be avoided. http://www2.ee.ntu.edu.tw/~b1901050/16-05-06_0055.jpg As an example, consider the LC oscillator shown above. It is desirable to maximize the voltage swings at nodes X and design of the stage(s) driven by the VCO. On the other hand, to avoid forward-biasing the varactors significantly, Vx and Vy must remain above approximately Vcont - 0.4V. Thus, the peak-to-peak swing at each node is limited to about 0.8V. Note that the cathode terminals of the caractors also introduce substantial n-well capacitance at X and Y, further constraining the tuning range. In contrast to pn junctions, MOS varactors are immune to forward biasing while exhibiting a sharper C-V characteristic and a wider dynamic range. If configured as a capacitor(as below), a MOSFET suffers from both a nonmonotonic C-V behavior and a high channel resistance in the region between accumulation and strong inversion. To avoid these issues, an "accumulation-mode" MOS varactor is formd by placing an NMOS device inside an n-well...... http://www2.ee.ntu.edu.tw/~b1901050/16-05-06_0056.jpg http://www2.ee.ntu.edu.tw/~b1901050/16-05-06_0057.jpg --

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