EE 420L Engineering Electronics II Lab - Project

Authored by Sergio Covarrubias

covars1@unlv.nevada.edu

05/03/2016

First Attempt
I started my project with a simple PUSH-PULL amplifier using both ZVN3306A and ZVP3306A with can acomplish great amouts of gain and good swing as I needed to acomplish a 30K gain which would drive a 10,000 Ohm load.
The first thing I did was to work on the LTspice simmulation showed on the screen capture bellow.



At first I started with PUSH-PULL with only 1 Nmos and 1 Pmos with a 10k Ohm input resitor and a 30K Ohm gain resistor. I noticied that buy adding Nmos and Pmos in parallel it increased the swing voltage by about 0.5V for each set I added. When I got to 8 Nmos and 8 Pmos I had a swing from 2.4v to 7.2v, I also though that I was going to have problems on the BreadBoard in terms of running out of room. The set up shown above I also had a great gain which was not affected by the number of Nmos and Pmos. I was happy with the simmulated results so I went ahead and built the circuit.

I layed out my circuit the way I had room to add or remove transistors as needed, I also like to make my circuits as simmilar as posible to the LTspice schematic. As soon as I connected my circuit I started having problems with noice and the experimental results did not match the LTspice simmulation at all. I checked my circuit over and over again, I thought I made a mistake when I wired my circuit.

I also had problems with overheating and the current being pulled from the Power Supply was huge. I started by removing Nmos and Pmos one by one which made my current go down but the noice issue did not get better, I noticed that by adding a capacitor on the top main power rails my osciloscope reading would jump around and would actually change drastically. When I went down to only 1 Nmos and 1 Pmos I still had lots of noice which made my input voltage (shown above CH1 yellow) and also on the output swing voltage (shown above on CH4 blue).


Second Attempt
After looking at my circuit for hours and experimenting with different number of Nmos and Pmos in parallel I finally noticed that the noice produced on the "first attempt" circuit was comming from the extended layout with all the jumpers that were necesary to be able to connect multiple Nmos and Pmos in parallel. I started from scratch in as compact as possible design, my new design allowed me to connect only 1 Nmos and 1 Pmos as shown on the screen capture bellow.

The calculated gain is purelly obtained from the gain resistor in my simulations labeled R1.

Circuit	Swing without a load at 1kHz.	Swing with load at 1kHz.	Swing with load at 100Hz.
	CH1=720mV CH2=480mV CH4=5.80V	CH1=720mV CH2=480mV CH4=5.60V	CH1=720mV CH2=5600mV CH4=5.00V
	Swing= 5.8 volts	Swing= 5.6 volts	Swing= 5.0 volts
	Calculations CH1(yellow)----Vs CH2(blue)-------VafterRin CH4(green)------Vout Gain=(Vout)/((Vs-VafterRin)/(Rin)) Gain=(5.8v)/((0.720v-0.480v)/(1K Ohm))=24.2K GAIN=24.2K	Calculations CH1(yellow)----Vs CH2(blue)-------VafterRin CH4(green)------Vout Gain=(Vout)/((Vs-VafterRin)/(Rin)) Gain=(5.6v)/((0.72v-0.48v)/(1K Ohm))=23.33K GAIN=23.33K	Calculations CH1(yellow)----Vs CH2(blue)-------VafterRin CH4(green)------Vout Gain=(Vout)/((Vs-VafterRin)/(Rin)) Gain=(5.0v)/((0.72v-0.56v)/(1K Ohm))=31.25K GAIN=31.25K

Third Attempt
On the "second attempt" circuit I had a great swing with almost 30K gain with and without load which could run on 100Hz and also at very high frequencies. I wanted to be able to produce more that 30K gain so I replaced the 30K Ohm gain resistor and replaced it with a 33K Ohm gain resistor which allowed me to make over 36K gain even driving the load at 1000Hz with would do 33.8K gain and with the load and 100Hz frequency it ran at 36.25K gain. I noticed that when using lower frequencies the gain would slightly increase.



In the LTspice simulations I had a Vout swing from 0.5v to 9.0v getting a 8.5v swing, this is a great swing covering almost all VDD.

Using A 33K Ohm gain resistor

Circuit-Board	Swing without a load at 1kHz.	Swing with load at 1K HZ.	Swing with load at 100 HZ.
	CH1=640mV CH2=480mV CH4=5.80V	CH1=640mV CH2=480mV CH4=5.40V	CH1=720mV CH2=560mV CH4=5.80V
	Swing= 5.8 volts	Swing= 5.4 volts	Swing= 5.8 volts
	Calculations CH1(yellow)----Vs CH2(blue)-------VafterRin CH4(green)------Vout Gain=(Vout)/((Vs-VafterRin)/(Rin)) Gain=(5.8v)/((0.64v-0.480v)/(1K Ohm))=36.3K GAIN=36.3K	Calculations CH1(yellow)----Vs CH2(blue)-------VafterRin CH4(green)------Vout Gain=(Vout)/((Vs-VafterRin)/(Rin)) Gain=(5.4v)/((0.64v-0.480v)/(1K Ohm))=33.8K GAIN=33.8K	Calculations CH1(yellow)----Vs CH2(blue)-------VafterRin CH4(green)------Vout Gain=(Vout)/((Vs-VafterRin)/(Rin)) Gain=(5.8v)/((0.720v-0.56v)/(1K Ohm))=36.2K GAIN=36.2K

Return to COVARS1 Homepage

Return to EE 420L Labs