The effect of parasitic capacitances on the circuit speed of GaAs MESFET ring oscillators

Circuit parasitic capacitances for GaAs ring oscillators (ROs) are calculated and used for SPICE2 circuit simulation. The simulated delays are found to agree with the measured data to within approximately 10%. The results are seen as suggesting that the effect of the circuit parasitic capacitances is dominant in determining circuit speed for high-density IC's at the microwave frequency. Minimization of the parasitics by using simpler cell designs and/or by further optimizing cell layouts, rather than by reducing the gate length, is thought to be the most fruitful approach for improving the circuit speeds.