Proposed Oscillator Topologies

A Colpitts oscillator (CO) is made up of an amplifier and a feedback network, consisting of an inductor and two capacitors. The feedback network is employed to direct a portion of the output signal back to the input through one of the reactive elements. Usage of feedback network provides both the frequency selection and signal reinforcement (positive feedback). For a CO, the oscillation frequency is dependent on its tank circuit elements L and the capacitive divider circuit, as given below.
\(f_{\text{osc}}=\frac{1}{2\pi\sqrt{LC_{t}}}\) and\(C_{t}=\frac{C1\ C2}{C1+C2}\)
The MOS based o8oscillator can be analyzed by using its tap ratio that is given by:
\begin{equation} n=1+\frac{C_{2}}{C_{1}}\nonumber \\ \end{equation}

Integer order Colpitts Oscillator

Initially, in this work, we design and simulate a conventional MOSFET (32 nm technology node) based single ended CO, as shown in Figure 8. In simulations a 32nm PTM model of MOSFET (L=32 nm and W=180 nm) has been used, along with RL=1kΩ, C1=C2=0.3n and Ibias=5mA. The value of inductor has been varied (keeping other parameters same) to check its effect on the oscillation frequency. The oscillation frequency is 1.2GHz for L=100p and 13.11 GHz for L=1p. Scaling down one of the elements of the tank circuit has a huge impact on its circuit oscillation frequency. On performing the transient analysis with both L=100pH and L=1pH, decaying oscillations can be observed with peak at approximately 0.999 Volts, as shown in Figure 9(a,b).