ecen 248 lab2_report

8/10/2019 ECEN 248 Lab2_report

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Lab 2: InverterCharacteristics and the

Ring OscillatorDeanna Sessions

ECEN 248- 511TA: Priya Venkatas

Date: September 16, 2013


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Objectives:In the first experiment in this lab I will learn about how the output voltages change in correlationto the input voltages in a logic gate. This will help to better understand what happens in the in-

between voltages when it is not strictly a high or low input. The second experiment in this

lab will teach how to create an oscillating voltage output just by using a series of NOT gates and

how to properly wire a SN7404 while creating this ring oscillator. More importantly, this willteach how to use the oscilloscope properly and read information off of it to collect data.

Design:Experiment 1:

Experiment 1 requires one inverter, a power source, and a multimeter. This was just an inverter

hooked up to an adjustable power source and a multimeter and the power source was

incrementally changed and the voltage output was recorded.

Experiment 2:

Experiment 2 requires one SN7404 which houses 5 NOT gates, a power source, a mutlimeter,

and an oscilloscope. The design of this circuit is included in the lab manual.

Results:Experiment 1:

Vin Vout

0 3.9

1 3.77

1.2 2.77

1.4 0.67

1.6 0.0975

1.8 0.0974

2 0.0975

3 0.0975

4 0.0974

5 0.0974

This data shows that for the input voltages of 0-1 V the setup is solidly showing a Logic 1

output, but at about 1.3 V there is a significant drop to having Logic 0 as an output and itstabilizes at 1.6 V to being consistently giving the same value of Logic 0 from 1.6 5 V. This

was an interesting thing to learn because I had expected it to return a Logic 0 closer to 1 V thanto 2 V because I had assumed any amount of voltage would return a Logic 0 from an inverter.

However, it makes sense that it would give a Logic 0 after having just passed 1 V because it

wouldnt be feasible to have the only way to get a Logic 0by having zero voltage attached to thecircuit.

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 1 2 3 4 5 6

VoltageOut

put(V)

Voltage Input (V)

Voltage Transfer Characteristics


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Questions:

1.

The graph above depicts the ranges for voltages in which Logic 1 and Logic 0 are shown. The

range of input voltage for which the inverter shows Logic 1 as output is 0 1 V and the range of

input voltage for which the inverter shows Logic 0 as the output is 1.65 V.

2. As shown above in the results section of the lab, the single stage delay of the Ring Oscillator

can be calculated using this equation:

Dinv=

This comes out to have an inverter delay equaling 5.94 ns for my particular ring oscillator with 5

NOT gates. The question suggests a 21 stage ring oscillator with Dinvequaling 10 ns and asks

what the frequency would be. Using the above equation coupled with f= 1/T you are able to

calculate that the period is 420 ns and that makes the frequency of this 21 stage Ring Oscillator

2.38 * 106Hz.

3. The signals at P, Q, R, and S are periodic and they have a time period of 5.94 ns which is the

same time as the delay and this should not differ from the signal at node A because node A is just

another gate exactly like the other 4.

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 1 2 3 4 5 6

VoltageOutput(V)

Voltage Input (V)

Voltage Transfer Characteristics

Logic 0Logic 1


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Student Feedback:

1. I really liked that this lab went more into the inner workings of the logic gates. I didnt

like how I didnt know how to properly wire an SN7404 or use an oscilloscope properly

and had to muddle through it a bit.

2.

I wish the manual told what pins connect with the other pins to create the internal NOTgates for the SN7404 because I didnt intuitively know that certain pins must be skipped

and gone back to in order to create the proper wiring. This part of the experiment could

have been made better if there were a better overview of the proper usage of the

oscilloscope. I also wish question 3 in the post-lab deliveries was more straightforward as

to what it is specifically wanting.

3. Include a diagram of how to properly wire the SN7404, include a comprehensive tutorial

on how to properly use the oscilloscope and get the data to look the way it is supposed to

look with the settings, and reword Post-Lab Deliverables #3.

ecen 248 lab2_report

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