Question

(a) Define propagation time $t_{PHL}$ for falling logic transitions, making clear how it differs from fall time. (b) A PMOS logic NOR gate uses a passive pull-down resistor of value 10k$\Omega$ and drives a load capacitance of 8pF. Estimate the propagation time $t_{PHL}$. (c) A single npn bipolar junction transistor with a passive pull-up is used as a logic invertor driving a stray capacitance load of 12pF. The supply voltage and the logic HIGH input voltage ($V_{IH}$) are both +5.0V. The input voltage is applied to one end of a 47k$\Omega$ resistor; the other end of the resistor is connected to the base terminal of the transistor. The transistor has a current gain ($\beta$ or $h_{FE}$) of 30 and its base-emitter junction has turn-on voltage $V_{on}$ = 0.7V. Estimate the propagation time $t_{PHL}$.

          (a) Define propagation time $t_{PHL}$ for falling logic transitions, making clear how it differs from fall time.
(b) A PMOS logic NOR gate uses a passive pull-down resistor of value 10k$\Omega$ and drives a load
capacitance of 8pF. Estimate the propagation time $t_{PHL}$.
(c) A single npn bipolar junction transistor with a passive pull-up is used as a logic invertor driving a
stray capacitance load of 12pF. The supply voltage and the logic HIGH input voltage ($V_{IH}$) are both
+5.0V. The input voltage is applied to one end of a 47k$\Omega$ resistor; the other end of the resistor is
connected to the base terminal of the transistor. The transistor has a current gain ($\beta$ or $h_{FE}$) of 30 and its
base-emitter junction has turn-on voltage $V_{on}$ = 0.7V. Estimate the propagation time $t_{PHL}$.

(a) Define propagation time tPHL for falling logic transitions, making clear how it differs from fall time.
(b) A PMOS logic NOR gate uses a passive pull-down resistor of value 10kΩ and drives a load
capacitance of 8pF. Estimate the propagation time tPHL.
(c) A single npn bipolar junction transistor with a passive pull-up is used as a logic invertor driving a
stray capacitance load of 12pF. The supply voltage and the logic HIGH input voltage (VIH) are both
+5.0V. The input voltage is applied to one end of a 47kΩ resistor; the other end of the resistor is
connected to the base terminal of the transistor. The transistor has a current gain (β or hFE) of 30 and its
base-emitter junction has turn-on voltage Von = 0.7V. Estimate the propagation time tPHL.

Added by Nicole G.

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