Introduction: Digital Logic Gates (Part 1)
In this instructable, we will get into IC chips and simple digital logic gates.
This is my first instructable; any feedback is greatly appreciated and please feel free to send me a message with any question you might have. Enjoy!
Press the following link for the second part: Digital Logic Gates (Part 2)
Step 1: Theory
The picture above depict IC's; an IC, Integrated Circuit, chip is a small electronic circuit that comprises of resistors, capacitors, diodes and transistors. IC's are made of silicon, a semiconducting material, and this is helps in compacting all the components together on a single chip utilizing tiny n-type and p-type silicon structures that get embedded to the chip in the manufacturing process. Also, it is important to note that the surface of a chip is plated with aluminum, which creates a connection between the components mentioned above. In this intractable, the three main digital logic gates ( NOT, AND, OR) will be explained thoroughly and demonstrated on a breadboard.
3 IC Chips: 74LS04, 74LS08, 74LS32
One 330 Ohm resistor
Wires as needed
Step 2: NOT Gate (Inverter)
An inverter (NOT Gate) implements logical negation. As shown in the truth table in Figure 2, if the input is Low (0) then the output will be High (1) and vice versa. In other words, the inverter's output is the compliment of the input. Thus, Q = A̅ (the bar means compliment). The 74LS04 is an IC chip that comprises of 14 pins; six inverters, supply voltage (Vcc) and ground (GND). Furthermore, we are going to test the inverter by constructing a simple circuit and observing the output using an LED detector circuit; if the LED is on then the output = 1 and if the LED is off then the output = 0. For the 74LS04 chip used, the supply voltage (Vcc) should be between 4.75V and 5.25V in order for the chip to function properly. In Figure 4, the input (A) = 0 and the output (Q) = 1. In Figure 5, the input (A) = 1 and the Output (Q) = 0.
Step 3: AND Gate
The AND gate implements logical conjunction; the output is High (1) only when both inputs are High and that can be seen in the truth table shown in Figure 2. The boolean expression for the AND operation is: Q = A . B
Another way to think of this is that the output of an AND gate is the minimum of the inputs; the AND gate finds the minimum of two bits. Also, the 74LS08 has 14 pins; four 2 input AND gates, a supply voltage (Vcc) pin, and a ground (GND) pin. The supply voltage (Vcc) should be between 4.75V and 5.25V in order for the IC to function properly. It is crucial to note that the only time the output of an AND gate is High (1) only when both inputs are High (1), as shown in Figure 7. Furthermore, for the breadboard part of this step, the blue wire is Input 1 (A), the white wire is the Input 2 (B), and the LED is the output.
Step 4: OR Gate
The OR gate implements logical disjunction; the result is High (1) when one or both of the inputs are High (1) just as seen in the truth table shown in Figure 2. Also, the boolean expression of the OR operation is: Q = A + B
An easier way to think of the OR gate is that its output is the maximum of the inputs. Also, the 74LS32 has 14 pins; four 2 input OR gates, a supply voltage (Vcc) pin, and a ground (GND) pin. The supply voltage (Vcc) should be between 4.75V and 5.25V in order for the IC to function properly. Furthermore, for the breadboard part of this step, the blue wire is Input 1 (A), the white wire is the Input 2 (B), and the LED is the output.