Consider the inverter below, whose output has falling and rising transitions due to the step input provided by the timing diagram below. a) In the average current method, the falling transition (propagation) delay is calculated by averaging the currents at point "A" (t = 0+, vo = VDD) and point "B" (t = tPHL, vo = VDD/2). Delta V is the voltage difference between point "A" and point "B". tPHL = C times Delta V/Iav, Iav = IA + IB/2 C = 5 fF (5*10^-15 F), V_D = 1.2 V, Vt = 0.3V, unCox = 300 uA/V^2. For QN transistor, (W/L) = 10. Find the currents at points A and B, and use the average current method to calculate the high-to-low inverter propagation delay (tPHL).
b) In the RC time constant method, the transition (propagation) delay is calculated by: tp = 0.69*R*C where R is found as either RN or Rp below, depending upon whether the output transition is high-to-low or low-to-high. RN = 12.5/(W/L)n kohm RP = 30/(W/L)p kohm Use the RC time constant method to calculate the high-to-low inverter propagation delay (tpHL).