LogicGates, Transistors & its Applications

1 Mark Questions

1.In a transistor, doping level in base is increased slightly. How will it affect

(i)collector current and

(ii)base current? [Delhi 2011]

Ans.(i) Collector current decreases.

1. Base current increases

2.Draw the logic circuit of a NAND gate and write its truth table.[Foreign 20113] Ans.

Logic circuit of a NAND gate ٠. Truth table

A В <math>Y = \overline{A \cdot B}</math> 0 0 0 1 0 NAME AND ADDRESS OF TAXABLE 1 0

<math display="block">(1/2\times 2=1)</math>

3.Draw the logic circuit of AND gate and write its truth table.[Foreign 2011] Ans.

Logic circuit of a AND gate

Truth table

Α В <math>Y = AB</math> 0 0 0 . . . . . . . . . . . 0 0 4 10 10 1 0 0 1

4.Draw the logic circuit of NOT gate and write its truth table.[Foreign 2011] Ans.

Logic circuit of a NOT gate

Truth table

A <math>Y = \overline{A}</math> 0 1 0

5. Write the truth table for the following circuit. Name the equivalent gate that this circuit represents.

<math>A \circ</math> οУ B • _____

[Foreign 2010]

Ans.

The given combination consists of NOR gate and NOT gate, so equivalent gate is OR gate.

Truth table

A В <math>Y = A + B</math> 0 0 0 0

<math display="block">(1/2\times 2=1)</math>

From the truth table, it is clear that the output is 1 only when at least one of the inputs is at the high state i.e. 1

1. The truth table of a logic gate has the form given here. Name this gate and draw its symbol.

A В Y

0 0 O o 0 1 1 0

[All India 2010C]

Ans.

Logic gate is NOR gate.

Symbol

1. The truth table of a logic gate has the form given here. Name this gate and draw its symbol.

Α В Y

0 0 ი 0 0

[All India 2010C]

Ans.

Logic circuit of a NAND gate ٠ Truth table

A В <math>Y = A \cdot B</math> 0 0 0 0 0

<math display="block">(1/2\times 2=1)</math>

8. Give the logic symbol of NOR gate. [All India 2009]