Lesson 14 Practice Problems Key – Transistors and Digital Logic 1#
Practice Problem 1 Solution#
How many transistors does it take to build the following circuit?
Using the simplified counting model shown in class and in the note-taker key, the total transistor count is:
Answer: 13 transistors
Practice Problem 2 Solution#
Reasoning (from the note-taker key):
Input B goes directly into the final OR gate, so whenever B = 1, the output is 1.
The AND gate can only output 1 when the NOT gate output is 1 and B is 1. Since the NOT is on A, that means A must be 0, and B must be 1.
Truth table:
A |
B |
Out |
|---|---|---|
0 |
0 |
0 |
0 |
1 |
1 |
1 |
0 |
0 |
1 |
1 |
1 |
Practice Problem 3 Solution#
This is a 3-input logic diagram, so there are 8 input combinations.
From the note-taker key:
The output can only be 1 when A = 1, B = 1, and C = 0.
Truth table:
A |
B |
C |
Out |
|---|---|---|---|
0 |
0 |
0 |
0 |
0 |
0 |
1 |
0 |
0 |
1 |
0 |
0 |
0 |
1 |
1 |
0 |
1 |
0 |
0 |
0 |
1 |
0 |
1 |
0 |
1 |
1 |
0 |
1 |
1 |
1 |
1 |
0 |
Practice Problem 4 Solution#
Reasoning (from the note-taker key):
The final gate is an OR gate, so any input of 1 gives Out = 1.
B is directly connected to the final OR gate, so anytime B = 1, Out = 1.
There is a NOT gate on the output of an AND gate. If the AND output is 0, the NOT output is 1, which then drives the OR to 1.
Truth table:
A |
B |
Out |
|---|---|---|
0 |
0 |
1 |
0 |
1 |
1 |
1 |
0 |
1 |
1 |
1 |
1 |