Electronically Tunable RC Sinusoidal Oscillators

This paper presents two types of active configurations for realizing electronically tunable RC sinusoidal oscillators. The type-1 network employs two grounded scaled resistances KR1 and KR2, where K is a scaling factor. The frequency of oscillation Wo is controlled conveniently by adjusting K, since Wo appears in the form W0 = l/K/√R1C1R2C2. For realizing the scaled resistances, an active configuration is proposed, which realizes KRi = Ri/1 + f(VB), where f(VB) denotes a function of a controlling voltage VB. Thus the frequency tuning can be effected by controlling a voltage VB. The type-2 oscillator uses two periodically switched conductances. It is shown that the tuning of oscillation frequency can be done by varying the pulsewidth-to-period ratio (τ/T) of the periodically switched conductances.