Novel Third–Order Quadrature Oscillators with Grounded Capacitors

This paper presents two Current Differencing Transconductance Amplifiers (CDTA)–based current–mode resistors–less variable frequency third–order Quadrature Oscillators (TOQO). The proposed TOQOs consist of minimum number of active and passive components, especially the first TOQO, only two CDTAs and three capacitors are used in it. The two TOQOs are completely resistor–less, and the capacitors used in the TOQOs are all grounded, which are ideal for monolithic integration. The condition of oscillation (CO) and frequency of oscillation (FO) of the TOQOs can be controlled electronically and independently, which make them suitable for variable frequency oscillator (VFO). Moreover, the two TOQOs can provide four explicit quadrature current outputs at high output impedance terminals, and they can be directly cascaded with other current–mode circuits without any impedance matching requirements. Cadence IC Design Tools 5.1.41 post–layout simulation results and experimental evidence are included to confirm all the theory.