lab 2

ELEC201 Digital Electronics

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Excelsior College

Module 2: Laboratory1: Basic Logic Gates

Objectives

The objectives of this experiment are to:

• Examine the operation of each basic logic gate. • Learn how to determine when a gate is malfunctioning.

Introduction

All digital circuits are composed of combinations of basic logic gates. Even such complex devices as microprocessors are built up from groups of logic gates. In this experiment you will verify the operation of several basic gates and see how truth tables are used to determine if a gate is operating correctly.

Procedure

1. Load the circuit E3-1.MS7, shown in Figure 3.1.

Figure 3.1: Inverter test circuit

2. The switch is used to apply logic zero and logic one values to the inverter. As shown, the switch is applying a logic zero, which causes the inverter to output a logic one, turning on the logic indicator. Pressing the ‘A’ key causes the switch to change positions. Verify that the circuit is operational by toggling the switch back and forth.

3. Fill in the truth table for the inverter based on the operation of the circuit. Record a zero for A or F if its associated logic indicator is off, and record a one if it is on.

A F

0

1

Table 3.1: Truth table for the inverter

Module 2: Laboratory1: Basic Logic Gates

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4. Load the circuit file E3-2.MS7. You should see the circuit shown in Figure 3.2.

Figure 3.2: AND gate test circuit

5. To test the 2-input AND gate you must apply four different patterns (00, 01, 10, and 11). Verify the operation of the AND gate and fill in its truth table.

A B F

0 0

0 1

1 0

1 1

Table 3.2: Truth table for the AND gate

6. Replace the AND gate with an OR gate and complete its truth table.

A B F

0 0

0 1

1 0

1 1

Table 3.3: Truth table for the OR gate

Module 2: Laboratory1: Basic Logic Gates

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7. Replace the OR gate with a NAND gate and fill in its truth table.

A B F

0 0

0 1

1 0

1 1

Table 3.4: Truth table for the NAND gate

8. Replace the NAND gate with a NOR gate and fill in its truth table.

A B F

0 0

0 1

1 0

1 1

Table 3.5: Truth table for the NOR gate

9. Replace the NOR gate with an exclusive OR gate and fill in its truth table.

A B F

0 0

0 1

1 0

1 1

Table 3.6: Truth table for the exclusive OR gate

10. Replace the exclusive OR gate with an exclusive NOR gate and fill in its truth table.

A B F

0 0

0 1

1 0

1 1

Table 3.7: Truth table for the exclusive NOR gate

Module 2: Laboratory1: Basic Logic Gates

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Discussion

While reviewing your data and results, provide detailed answers to each of the following:

1. What is the relationship between the AND gate and the NAND gate?

2. What would happen if two inverters were connected in series?

3. Which gate outputs a zero only when both inputs are high?

4. Which gate outputs a zero when both inputs are the same logic level?