Half-life of a radioactive substance is 20 min. The time between 20% and 80% decay will be

• 20 min

• 30 min

• 40 min

• 25 min

Which type of gate the following truth table represents ?

• NOT

• AND

• OR

• NAND

In a n-type semiconductor, which of the following statement is true ?

• Electrons are majority carriers and trivalent atoms are dopants

• Electrons are minority carriers and pentavalent atoms are dopants

• Holes are minority carriers and pentavalent atoms are dopants

• Holes are majority carriers and trivalent atoms are dopants

In a common emitter (CE) amplifier having a voltage gain G, the transistor used has transconductance 0.03 mho and current gain 25. If the above transistor is replaced with another one with transconductance 0.02 mho and current gain 20, the voltage gain will

• $\frac{2}{3} \mathrm{G}$

• 1.5 G

• $\frac{1}{3} \mathrm{G}$

• $\frac{5}{4} \mathrm{G}$

The output (X) of the logic circuit shown in figure will be

• $\mathrm{X} = \stackrel{=}{\mathrm{A}} . \stackrel{=}{\mathrm{B}}$

• $\mathrm{X} = \overline{\mathrm{A} . \mathrm{B}}$

• X = A .B

• $\mathrm{X} = \overline{\mathrm{A} + \mathrm{B}}$

The output (X) of the logic circuit shown in figure will be

• $\mathrm{X} = \stackrel{=}{\mathrm{A}} . \stackrel{=}{\mathrm{B}}$

• $\mathrm{X} = \overline{\mathrm{A} . \mathrm{B}}$

• X = A .B

• $\mathrm{X} = \overline{\mathrm{A} + \mathrm{B}}$

The output Y ofthe logic circuit given below is

• $\overline{\mathrm{A}} + \mathrm{B}$

• $\overline{\mathrm{A}}$

• $\overline{\left(\overline{\mathrm{A}} + \mathrm{B}\right)} . \overline{\mathrm{A}}$

• $\overline{\left(\overline{\mathrm{A}} + \mathrm{B}\right)} . \mathrm{A}$

In the bandgap between valence band and conduction band in a material is 5.0 eV, then the material is

• semiconductor

• good conductor

• superconductor

• insulator

In a transistor output characteristics commonly used in common emitter configuration, the base current I_B, the collector current l_C and the collector emitter voltage V_CE have values of the following orders of magnitude in the active region

• I_B and I_C both are in µA and V_CE in volt

• I_B is in µA and I_C is in mA and V_CE in volt

• I_B is in mA and I_C is in µA and V_CE in volt

• I_B is in mA and I_C is in mA and V_CE in mV

The inputs to the digital circuit are as shown below. The output Y is

• $\mathrm{A}\hspace{0.17em}+ \mathrm{B} + \overline{\mathrm{C}}$

• $\left(\mathrm{A}\hspace{0.17em}+ \mathrm{B}\right) \overline{\mathrm{C}}$

• $\overline{\mathrm{A}} + \overline{\mathrm{B}} + \overline{\mathrm{C}}$

• $\overline{\mathrm{A}} + \overline{\mathrm{B}} + \mathrm{C}$