ECE 248
Lab 4 Report
Spring 2014
Title
Author
Your Major, Union College, Schenectady, NY 12308
ABSTRACT
This is the template for your lab report. Margins are 1-inch all around. All text is in Times New Roman
font with a line-spacing of 1.5. The title is bold-faced, 18 pt, and centered. All other text is in 11 pt font.
The author is bold-faced and centered. The author affiliation is also centered. Each page should have a
header and page number. The abstract should be short (seven lines or so). It summarizes the purpose of
your lab work (e.g. understand an emitter follower), what you actually did (e.g. built a Darlington
follower), noteworthy results (e.g. speaker made sound!). The last sentence or two should describe your
opinion on how you benefited from the lab (e.g. appreciate the importance of voltage buffers).
INTRODUCTION
Briefly give a background (a few sentences) for each of the following main topics of Lab 4:
1) Voltage Buffer: Describe the purpose of a voltage buffer.
2) Zener Follower: Describe the purpose of an emitter follower in a zener-based DC power supply.
3) Speaker Driver: Describe the purpose of a Darlington-based emitter follower in a speaker driver.
EXPERIMENTS AND RESULTS
Circuit 1: Zener Follower

Circuit schematic (OK to use your prelab schematic).

Experimental zener voltage (VB of transistor) and load voltage (VE of transistor).

Based on your measured zener voltage, was the zener working properly (e.g. not in drop out)?

Show your calculations for the load current (IE of transistor).

Show your calculations for the transistor power dissipation.

Measured voltage when the motor was directly attached to the zener.
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ECE 248
Lab 4 Report
Spring 2014
Circuit 2: Audio Speaker

Circuit schematic (OK to use your prelab schematic).

Simulated voltage waveforms.

Simulated voltage gain VOUT/VS (should be near 0.015).

Experimental voltage waveform for VOUT.

Experimental peak-to-peak VOUT.

Experimental voltage gain VOUT/VS.

Percent disagreement between experiment and simulation for voltage gain.

How good is the agreement between experiment and simulation?
Circuit 3: Speaker Driver

Circuit schematic (OK to use your prelab schematic).

Simulated voltage waveforms.

Simulated voltage gain VOUT/VIN and VOUT/VS.

Simulated input impedance RIN.

Experimental voltage waveforms for VOUT and VIN.

Experimental peak-to-peak VOUT and VIN.

Experimental voltage gain VOUT/VIN and VOUT/VS.

Experimental input impedance RIN.

Percent disagreement between experiment and simulation for VOUT/VIN, VOUT/VS, and RIN.

How good is the agreement between experiment and simulation?
DISCUSSION
Please provide answers (few sentences each is OK) to the following questions. DO NOT INCLUDE THE
QUESTIONS IN YOUR REPORT. Just provide the answers.

Zener follower
Although the emitter follower can drive the motor with the required current, the transistor does get
pretty warm due to power dissipation. Suppose a current-hungry load causes the transistor to get
really hot (e.g. burn your finger). Describe TWO strategies to address this undesirable situation (e.g.
prevent overheating).
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ECE 248

Lab 4 Report
Spring 2014
Darlington follower
No sound was produced when the speaker was directly attached to a high impedance source (function
generator + 1 kohm resistor). Using the Darlington-based emitter follower obviously produced a
beautifully audible sound. Suppose you decide to try a single-transistor emitter follower (e.g. only
using the 2N3904). Would this produce a sound level that is louder, the same, or softer than the
Darlington follower? Explain your reasoning.

Miscellaneous
Overall, did your circuits work the way you expected? Were there any peculiarities?
CONCLUSIONS
This is where you write about the concepts or any valuable lessons you learned in the lab. If possible,
discuss how they relate to other aspects of the course or to the general field of electronics. Your
conclusion section should NOT be a summary of your results or what tasks you performed. The
conclusion is supposed to reveal what you have learned from your lab experience.
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