Lab 7 - EE 420L
Authored
by Iain Drews, drewsi2@unlv.nevada.edu
4/9/2015
Lab
description
Design
an audio amplifier (frequency range from roughly 100 Hz to 20 kHz)
assuming that you can use as many resistors, ZVN3306A transistors, and
ZVP3306A transistors as you need along with only one 10 uF capacitor
and one 100 uF capacitor. Assume that the supply voltage is 10 V, the
input is an audio signal from an MP3 player (and so your amplifier
should have at least a few kiloohms input resistance), and the output
of your design is connected to an 8-ohm speaker (so, ideally, the
output resistance of your amplifier is less than 1 ohm).
- Your lab report should detail your thoughts on the design of the amplifier including hand-calculations.
- A good place to start is with the push-pull amplifier characterized in lab 6.
- We started with the Push-Pull amplifier but it has too high of an output resistance.
- so we added a Common Drain amplifier to have low output resitance.
- from there we just needed to find a balance between the two so we would have the gain and the low output resitance.
- we noticed that the DC current being sent through the mosfetts was quite high and causing them to generate quite a bit of heat so we added resistors on each end of the push-pull to reduce power consumption.
- we settled on the schematic below with R1 being a Potentiometer that so we can adjust the gain thereby giving us volume control.
| Schematic: note R1 in the circuit is a potentiometer. |  |
|  |
- Build and test your design.
- Document the performance of the design including power dissipation, output swing, input resistance, output resistance.
- VDD was 10V and Current draw was about 30mA so power dissapation was 300mW
- input resistance of the device is 1/gm1||1/gm2+5k or about 5044ohms
- the final output resitance of the divice is RSpeaker||1/gm3 gm3 is as follows so Rout is 8||(1/.119) or about 4 ohms.
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