True or False questions (1) For a NMOS, if the body voltage potential is lower t

Question

True or False questions

(1) For a NMOS, if the body voltage potential is lower than the source voltage potential, its threshold voltage will decrease as compared with the case when the source and the body has the same voltage potential. _______________

(2) For an inverter with NMOS as load, the highest output voltage is less than VDD, the lowest output voltage is larger than 0. ____________

(3) For a CMOS inverter, if NMOS and PMOS has the same threshold voltage (in absolute value), and also NMOS and PMOS has the same W/L, then the VM in the voltage transfer curve is VDD/2. _______________

(4) A CMOS inverter is driving an identical inverter, if the W/L of CMOS inverter in the first stage (including both NMOS and PMOS) doubles, the propagation delay in the first stage will be reduced to half of its original value. ____________________

(5) For a NMOS pass gate transistor, the highest output voltage is less than VDD, the lowest output voltage is larger than 0._______________________

Explanation / Answer

(1)

In normal MOSFET connections, the source and the body voltages are shorted.

This does not have any effect on the MOSFET threshold voltage.

If they are at differential potentials, that is the body is at a lower potential than the source voltage; then the source and substrate enter into reverse bias condition, with less voltage required than normal.

That is, the gate voltage normally applied is +ve for NMOS, for saturation.

The difference in the voltage results in reducing the voltage required to induce the accumulation and inversion.

Hence, the statement is true.

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