EE 231
Prelab 2: Basic Combinational Circuits using SSI IC's

Prelab for Part 1. A Simple Circuit.

Analyze the circuit shown in Figure 1 and complete the following tasks:

1. Determine and fill in its truth table.
2. Draw the output waveform (Y) for the given input (signals A, B, and C).
3. Complete the schematic by adding pin numbers and chip designators (U1 and U2). Use one 74HC04 hex inverter and one 74HC10 triple three-input NAND gate (NOTE: you will not find the 74HC10 in your ON Semiconductor data book).

Figure 1: Test Circuit for EE 231 SSI Combinatorial Circuits Lab.

Having the pin numbers on your schematic makes it much easier to wire and check the circuit. See the attached page for an example schematic. U1 and U2 are chip designators. Pin numbers are identified on the logic symbols, and chips are identified in the legend.

Prelab for Part 3. The Majority Circuit.

Three engineers work in a lab, and constantly fight over whether the radio should be on or off. They decide to build a circuit which will turn on the radio if a majority of the three want it on. Design a circuit to accomplish this - i.e., design a three-input, one-output circuit for which the output will be high if a majority of the three inputs are high.

To implement your design, you may use only 74HC00, 74HC02, 74HC04, 74HC08, 74HC10 and 74HC86 chips.
(NOTE: you will not find the 74HC10 in your ON Semiconductor data book)

Use your data book to find out what the following chips are:

• 74HC00 _____________________________________________________
• 74HC02______________________________________________________
• 74HC04______________________________________________________
• 74HC08______________________________________________________
• 74HC10______________________________________________________
• 74HC86______________________________________________________

Draw three representations for this design:

1. A three-input, one-output Truth table;
2. An input and output waveform sketch;
3. A schematic using gate symbols (as in Part 1.);

Don't forget to include pin numbers and chip designators.

Wiring even a small number of chips is a tedious error prone task. Also, fewer chips mean reduced cost and lower power consumption. Try to realize the circuit with a minimum number of chips.