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Silicon Carbide Oscillators for Extreme Environments
Published in Sumeet Walia, Krzysztof Iniewski, Low Power Semiconductor Devices and Processes for Emerging Applications in Communications, Computing, and Sensing, 2018
Daniel R. Brennan, Hua-Khee Chan, Nicholas G. Wright, Alton B. Horsfall
The Colpitts oscillator is a common form of LC oscillator that utilizes an LC tank circuit and an active device to counteract the damping effect caused by parasitic resistances. The Colpitts oscillator can be realized using a single transistor acting as an amplifier with the addition of a tank circuit. The circuits considered here are based on the use of a depletion mode SiC JFET; however, the analysis can be expanded to include a wide range of alternative transistor families, including MOSFETs and bipolar junction transistors (BJTs) as well as thermionic valves. By feeding the signal back from the output of the amplifier to the input through this LC tank to select a single frequency, it is possible to commission a Colpitts oscillator circuit, as shown by the circuit given in Figure 10.11.
Analogue systems and concepts
Published in Geoff Lewis, Communications Technology Handbook, 2013
Colpitts oscillator. The circuit of Fig. 1.30 depicts a popular RF oscillator that has good stability. The resonant frequency is controlled by L1 and C1 in series with C2. As connected, this provides zero loop phase shift marginally above the theoretical resonant frequency. The circuit is described as being shunt fed; the resonant circuit being in parallel with the active device relative to the dc power supply. The twin gang tuning capacitors with the grounded vanes ensure that hand capacity effects are minimal and they act as low impedance bypasses to earth for any harmonics, thus providing an output waveform of high purity.
Electronic Circuits
Published in Dale R. Patrick, Stephen W. Fardo, Electricity and Electronics Fundamentals, 2020
Dale R. Patrick, Stephen W. Fardo
A Colpitts oscillator is very similar to the shunt-fed Hartley oscillator. The primary difference is in the tank circuit structure. A Colpitts oscillator uses two capacitors instead of a divided coil. Feedback is developed by an electrostatic field across the capacitor divider network. Frequency is determined by two capacitors in series and the inductor.
Design of a new low-phase-noise millimetre-wave quadrature voltage-controlled oscillator
Published in International Journal of Electronics, 2018
Zeinab Kashani, Abdolreza Nabavi
The Colpitts oscillator has several advantages, such as better loaded quality factor, low signal distortion and better impulse sensitivity function (ISF) (X. Li, Shekhar, & Allstot, 2005). However, compared to the cross-coupled oscillator, a Colpitts VCO requires wider transistors to start oscillation due to the capacitive voltage division. This also reduces the negative resistance which is added to the tank per micron of transistor width (Kraemer, Dragomirescu, & Plana, 2011). Thereby, it is difficult to realise the conventional Colpitts oscillator in 60 GHz applications, and solving its start-up issues and improving the PN performance are important. As a result, the Colpitts oscillator is a good candidate for this work. Despite the cross-coupled oscillator, the Colpitts oscillator realises its positive feedback internally. Thus, it has undesirable common-mode stability issues (Wu & Luong, 2014). To suppress these unwanted common-mode oscillation, the common-mode point of the source degeneration capacitor in the source of the transistor can be floated. In this way, its common-mode capacitance is minimised, which ensures the common-mode stability. Since the oscillators oscillate out of phase, a virtual ground is created inside the capacitor, and hence no radio frequency (RF) ground currents have to circulate through this usually ground-connected capacitance (Fu, Ke, Kuo, Chiu, & Wu, 2010).
A 100-Mrad (Si) JFET-Based Sensing and Communications System for Extreme Nuclear Instrumentation Environments
Published in Nuclear Technology, 2022
F. Kyle Reed, M. Nance Ericson, N. Dianne Bull Ezell, Roger A. Kisner, Lei Zuo, Haifeng Zhang, Robert Flammang
The Colpitts oscillator, whose schematic is shown Fig. 2a, is a sinusoidal output oscillator that uses an inductance-capacitance (LC) tank network to provide the necessary phase shift to induce the required instability for oscillation. The frequency of the Colpitts oscillator is described by