Lab

Lab 7 - ECE 420L

Authored by Kyle Butler, butlerk2@unlv.nevada.edu

4/3/2019

Pre-lab work:

This lab will utilize the ZVN3306A and ZVP3306A MOSFETs.

Lab work:

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.

Simulate your design. Document the results in your lab report.
Build and test your design.
Document the perofrmance of the design including power dissipation, output swing, input resistance, output resistance.

Design Process
We will begin with the push-pull amplifier characterized in lab 6.

http://cmosedu.com/jbaker/courses/ee420L/s19/students/butlerk2/Lab%207/push_pull.JPG

http://cmosedu.com/jbaker/courses/ee420L/s19/students/butlerk2/Lab%207/push_pull_dc.JPG

http://cmosedu.com/jbaker/courses/ee420L/s19/students/butlerk2/Lab%207/push_pull_sim.JPG

Connecting the source directly to the speaker (Vout1) reduces the output voltage greatly and is essentially 0. When looking at the output of the push pull amplifier we can see some output voltage. We can calculate the gain of the push pull amplifier.
Additionally we should calculate the output resistance of the amplifier, ideally the output resistance of the designed amplifer should be 1.

Hanc Calculations:

http://cmosedu.com/jbaker/courses/ee420L/s19/students/butlerk2/Lab%207/handcalc.JPG

We are getting an output resistance of approximatly 8 Ohms, we can implement a source follower inorder to further reduce the output resistance.

However this assumption is made with an 8 Ohm speaker and for this lab we are using a 25 Ohm speaker. So the push pull orientation work better for this load.

Lets do some simulations to find a value for R1. We need to find a gain large enough to hear our signal, but not so large its causes some distortion.

http://cmosedu.com/jbaker/courses/ee420L/s19/students/butlerk2/Lab%207/design.JPG

http://cmosedu.com/jbaker/courses/ee420L/s19/students/butlerk2/Lab%207/design_sim.JPG

We decided to use a 20k resistor, it had a smooth reponse and it was the most available resistor in the lab. Now lets consider the reponse for the load resistor.

http://cmosedu.com/jbaker/courses/ee420L/s19/students/butlerk2/Lab%207/design2.JPG

http://cmosedu.com/jbaker/courses/ee420L/s19/students/butlerk2/Lab%207/design2_sim.JPG

One of the lower power consumption, but reasonable output is 20 Ohms. However we used 25 Ohms to match the speaker and because it was available in the lab

Now with 20KOhms for R1 and 25Ohms for R2 lets look at the input and output resistance respectively. Sims show ~23KOhm for input and 25Ohm for output.

http://cmosedu.com/jbaker/courses/ee420L/s19/students/butlerk2/Lab%207/input_res.JPG

http://cmosedu.com/jbaker/courses/ee420L/s19/students/butlerk2/Lab%207/output_res.JPG

Building Circuit
Response

100Hz 20KHz

http://cmosedu.com/jbaker/courses/ee420L/s19/students/butlerk2/Lab%207/100hz.JPG

http://cmosedu.com/jbaker/courses/ee420L/s19/students/butlerk2/Lab%207/20khz.JPG

Circuit Test with MP3

http://cmosedu.com/jbaker/courses/ee420L/s19/students/butlerk2/Lab%207/test.JPG

http://cmosedu.com/jbaker/courses/ee420L/s19/students/butlerk2/Lab%207/test_output.JPG

My output signal for 100Hz is 664mV and 944mV at 20KHz. My simulations for 100Hz showed approx. 350mV for a 1V input. While I did achieve a negative gain for a push pull amplifier correctly, for some reason when using the MP3 signal as input my gain was abnormally high.
I am assuming we shorted some connections when connecting out AUX cables. I was able to hear Hit'Em Up by 2PAC clearly through the speaker, but the signal generator had significantly more volume.

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