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Radio frequency heterojunctio bipolar transistor variable frequency oscillator and variable gain amplifier
本碩士論文包含可變頻率震盪器和可變增益放大器的實現和設計。在可變頻率震盪器設計中，設計出一個可以取代MOS可變電容的電路且全由NPN的BJT所組成。在磷化銦鎵/砷化鎵(GaInP/GaAs)製程中，只有NPN的BJT可以使用，所以這電路解決在磷化銦鎵/砷化鎵(GaInP / GaAs)製程中沒有可變電容的窘境。
在可變增益放大器設計中，利用兩級的電流鏡做為放大器，使用AC coupling 的方式把信號couple進來且把信號放大，中間級使用電流的方式把信號衰減，達到wide dynamic range的目的。
Fabricated through a GaInP/GaAs HBT technology, a monolithic variable frequency oscillator (VFO) and a monolithic variable gain amplifier (VGA) were measured and reported in this thesis. A number of issues on the VFO and VGA were detailed as well.
A new circuitry, called a Variable Impedance Converter (VIC), was adopted to mimic a variable capacitor, which was essentially an important element for frequency tuning in a LC-based oscillator design.A negative-impedance converter not only provides the necessary negative resistance for oscillation, but also functions as the voltage level shifters for the VIC. A classic circuit, called a translinear circuit, makes full advantage of the exponential I-V characteristic to linearize the tuning curve of the VFO. No external but two on-chip inductors were used in the VFO.
Several operating principles for a VGA were explored in the VGA chapter. Based these principles we discussed, a wide gain control range VGA was achievable. The designed VGA consisted of a fixed gain preamplifier, a variable attenuator, and a tunable transconductance common-emitter (CE) amplifier, in which the input impedance is also controllable by a voltage controlled resistor. Therefore, by cleverly composing these functions of the controllable components, a low noise VGA with 50dB gain control range result.
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