Electronically and Independently Controllable Quadrature Sinusoidal Oscillator with Low Output Impedances

Abstract

This work presents the quadrature si- nusoidal oscillator using two Voltage Differencing- Differential Input Buffered Amplifiers (VD-DIBAs), two resistors, and two capacitors. The VD-DIBA is an electronically controllable active building block with high input and low output impedances that can con- nect to other circuits directly without the buffers. With these distinguished features, the VD-DIBA is employed in this design. The proposed oscillator can produce two sine waves with a phase shift of 90 degrees. Over the entire tuning frequency range, the magnitude of the quadrature output voltages is constant. The pro- posed oscillator is independently adjustable in terms of frequency and oscillation condition. Moreover, the frequency of oscillation can be electronically and lin- early adjusted by the bias currents. The condition of oscillation is adjustable by resistors, R1 and R2. The performances of the proposed quadrature oscilla- tor are tested through the PSpice simulation and the experiment. In the simulation, the VD-DIBA is built from the 0.18 μm Taiwan Semiconductor Manufactur- ing Company (TSMC) CMOS process with ±0.9 V sup- ply voltages. In the experiment, the VD-DIBA is im- plemented using the commercial ICs, LM13700, and AD830 with ±5 V supply voltages. The simulated To- tal Harmonic Distortion (THD) values of the output voltages, Vo1 and Vo2 at f0 = 1.03 MHz are 1.63 % and 1.81 %, respectively. The experimental THD values of the output voltages, Vo1 and Vo2 at f0 = 536.6 kHz, are 1.43 % and 1.00 %, respectively.