A VHF Oscillator Design Based on BJT Active Load Differential Amplifier

In this paper, we present a VHF (Very High Frequency) band oscillator which mainly composed of a BJT active load differential amplifier (Diff. amp). We use H-spice to verify that the active load differential amplifier oscillator output frequency is 900 MHz at 2.0 volts power supply under CIC 0.18 um-Si process. We also use discrete devices on bread board to prove the circuit is an oscillator circuit. Those experiments show such an oscillator can work stably from 3.8 to 5.9 volts. Their output frequency will be 161.1 MHz, 186.7 MHz under 3.8 volts and 5.9 volts respectively. We use FFT (Fast Fourier Transform) diagram to analyse these oscillators and shows SNR (Signal-to-Noise Ratio) values. Finally, those experimental results reveal that the oscillator is a nice voltage controlled oscillator (VCO) and also have good SNR characteristics.