Loop Gain of the Common-Drain Colpitts Oscillator

Abstract

Loop Gain of the Common-Drain Colpitts OscillatorThis paper presents the derivations of the voltage transfer functions of the amplifier A, the feedback network β, and the loop gainTof the common-drain (CD) Colpitts oscillator, using the small-signal model of the CD Colpitts oscillator. The derivation of the characteristic equation of the CD Colpitts oscillator is presented. Using the characteristic equation, the equation for the oscillation frequency of the sinusoidal output voltage and the condition for steady-state oscillation are derived. The characteristic equation is used to obtain a plot of trajectories of the poles of the CD Colpitts oscillator by varying the MOSFET small-signal transconductancegm. The locations of the complex conjugate poles depicting starting and steady-state conditions for oscillations are also presented.

Design and simulation of high frequency colpitts oscillator based on BJT amplifier

“…In this design, voltage divider method as shown in Figure 1, is used because it has many advantage, such as good stability, the amplitude is not depending on change of β or resistors and easy control for biasing current. From theory of calculation of biasing resistors, there are some approximation can be used to reduce the steps of calculations [13]. Figure 1 shows the demonstration, of voltage divider biasing that used to obtain the correct operating point, so that the values of R 1 , R 2 , R C and R E can be calculated.…”

“…There are different types of these oscillator such as Colpitts oscillator Hartley oscillator, Clap oscillator, Armstrong oscillator and Crystal controlled oscillator [5,11]. The problem stetmant in the design of Collpits oscillator is that most of the present journal articals such as [12][13][14] also textbooks such as [15,16], used the formula. has been derivetave as novel exact formula.…”