An analytical treatment of the performance of submicrometer FET logic

A self-consistent periodic approach is presented for analyzing the waveforms and for obtaining an analytical expression for the propagation delay of a submicrometer expression for the propagation delay of a submicrometer FET ring oscillator. Rather than using a step input to the inverter to estimate the propagation delay, which greatly overestimates the propagation delay, or an arbitrary ramp input, the actual waveform input is used, which is generated from the periodic equations associated with the ring oscillator. The equations for the waveforms, propagation delay, dynamic transfer characteristics, and dynamic load lines are obtained in closed form in terms of the electrical parameters of the driver and load devices of the inverters. The calculated waveforms, propagation delays, etc. are compared with their computer simulations and the correlation is seen to be very good. Thus the analytical expressions permit a direct appreciation of the influence of the various device parameters on device performance, and as such provide useful information for the designer. The equations are used to analyze an actual 19-stage submicrometer silicon ring oscillator.