ECE 4104 (Logic Circuits and Switching Theory)

Experiment No. 1 DIODE AND TRANSISTOR LOGIC GATES

Submitted by: GROUP # 3 BURGOS, Arman DIOCADES, Erna Mae FAIGONES, Russel Lab. Schedule: Th 7:00 – 10:00 AM Date Submitted: June 18, 2012

Instructor: Engr. Ramon Alguidano Jr.

I.

OBJECTIVES 1) To be able to construct logic gate circuits, utilizing diode and transistors and observe its characteristics. 2) To be able to simulate diode and transistor gate circuit operations using any electronic simulation software. 3) To the truth table of the logic gates with the use of diode and transistor. 4) Be familiar with the diode & transistor logic gates and its circuit operation.

II.

BASIC THEORY

A logic gate is an idealized or physical device implementing a Boolean function, that is, it performs a logical operation on one or more logic inputs and produces a single logic output. They are primarily implemented using diodes or transistors acting as electronic switches

Digital logic gates process digital signals as input and produce a digital signal as output. Logic gates are an essential part of digital circuitry and are implemented using transistors or diodes.

Three common gates are: AND, OR, and NOT. These gates are represented by the following symbols:

Input and output signals are represented through several types of nomenclature: true/false, 1/0, on/off, high/low. The logic for each gate is often represented in a truth table. 

As the name implies, inverter will invert the number entered. If you enter “0”, you will get a “1” on its output, and if you enter a “1”, you will get a “0” on its output. AND gate always has a false output unless both inputs are true.



As the name implies, inverter will invert the number entered. If you enter “0”, you will get a “1” on its output, and if you enter a “1”, you will get a “0” on its output.



As the name implies, inverter will invert the number entered. If you enter “0”, you will get a “1” on its output, and if you enter a “1”, you will get a “0” on its output.

The following are the basic circuit of diode and transistor logic:

III.

SCHEMATIC DIAGRAM

IV.

EQUIPMENT/MATERIALS/COMPONENT NEEDED

V.

PROCEDURES AND RESULTS

1) Construct the circuit found in figure 1.1. 2) Connect the positive side of the diodes A and B to the S 1 and S2 terminal of the logic trainer. 3) Connect the output Y to the L1 of the trainer.  What Logic gate circuit was constructed?  Diode OR-gate circuit  After constructing the circuit, record its observed characteristics by filling up the truth table below.

Logic 1 = 5volts Logic 0 = 0volts

 Simulate the circuit using any electronic simulation software.

 Show the actual result.

4) Construct the circuit found in figure 1.2. Connect the negative side of the diodes A and B to the S1 and S2 terminal of the logic trainer. Connect the output Y to the L1 of the trainer.  What Logic gate circuit was constructed?  Diode AND-gate circuit  After constructing the circuit, record its observed characteristics by filling up the truth table below.

Logic 1 = 5volts Logic 0 = 0volts

 Simulate the circuit using any electronic software.

 Show the actual result.

5) Construct the circuit found in figure 1.3. Connect the base terminal of transistor A to S1 terminal of the logic trainer. Connect the output Y to the L1 of the trainer.  What Logic gate circuit was constructed?  Transistor Inverter Circuit

 After constructing the circuit, record its observed characteristics by filling up the truth table below. Logic 1 = 5volts Logic 0 = 0volts

 Simulate the circuit using any electronic software.

 Show the actual result.

6) Construct the circuit found in figure 1.1. Connect the base terminal of transistors A and B to the S1 and S2 terminal of the logic trainer. Connect the output Y to the L1 of the trainer.

 What Logic gate circuit was constructed?  Transistor OR-gate circuit  After constructing the circuit, record its observed characteristics by filling up the truth table below.

Logic 1 = 5volts Logic 0 = 0volts

 Simulate the circuit using any electronic software.

 Show the actual result.

7) Construct the circuit found in figure 1.1. Connect the base terminal of the transistors A and B to the S1 and S2 terminal of the logic trainer. Connect the output Y to the L1 of the trainer.  What Logic gate circuit was constructed?  Transistor AND-gate circuit  After constructing the circuit, record its observed characteristics by filling up the truth table below. Logic 1 = 5volts Logic 0 = 0volts

 Simulate the circuit using any electronic software.

 Show the actual result.

VI.

OBSERVATION

Conducting this experiment on diode and transistor logic gates, the group was able to observe the characteristics and behavior of the circuits found in figures 1.1, 1.2, 1.3, 1.4 and 1.5. The gathered data about the said circuits were recorded on the truth tables found every after each procedure. Further details about the results procured are described thoroughly below: DIODE “OR” GATE CIRCUIT (Figure 1.1) •

When terminals A and B of the circuit are supplied, there was no significant output observed at the terminal Y;

•

When either of the terminals A or B was supplied, it was observed that an output is likely to appear;

•

And, when both terminals A and B were supplied, an output was also recorded at terminal Y of the circuit.

GENERAL OBSERVATION for Figure 1.1 In order to have an output on this type of circuit, at least one diode terminal must be supplied. This is the very reason why the circuit on Fig. 1.1 is called Diode “OR” gate circuit. DIODE “AND” GATE CIRCUIT (Figure 1.2) •

When terminals A and B were not supplied, there was no observable output on

the terminal Y;

•

When either of the terminals A or B was supplied, still there was no observable output on the terminal Y;

•

But when both terminals A and B were supplied, an output was finally recorded.

GENERAL OBSERVATION for Figure 1.2 In order to have an output on this type of circuit, both diode terminals A and B must be supplied. This is the very reason why the circuit on Fig. 1.2 is called Diode “AND” gate circuit. TRANSISTOR INVERTER (Figure 1.3) •

In order to have an output on the terminal Y of this circuit, the base of the transistor must not be supplied, otherwise an opposite phenomena will occur.

TRANSISTOR “OR” GATE CIRCUIT (Figure 1.4) •

When terminals A and B of the circuit are supplied, there was no significant output observed at the terminal Y;

•

When either of the terminals A or B was supplied, it was observed that an output is likely to appear;

•

And, when both terminals A and B were supplied, an output was also recorded at terminal Y of the circuit.

GENERAL OBSERVATION for Figure 1.4

In order to have an output on this type of circuit, at least one terminal must be supplied. This is the very reason why the circuit on Fig. 1.4 is called Transistor “OR” gate circuit. TRANSISTOR “AND” GATE CIRCUIT (Figure 1.5) •

When terminals A and B were not supplied, there was no observable output on the terminal Y;

•

When either of the terminals A or B was supplied, still there was no observable output on the terminal Y;

•

But when both terminals A and B were supplied, an output was finally recorded.

GENERAL OBSERVATION for Figure 1.5 In order to have an output on this type of circuit, both diode terminals A and B must be supplied. This is the very reason why the circuit on Fig. 1.2 is called Transistor “AND” gate circuit.

VII.

CONCLUSION

VIII.

DESIGN PROBLEM