EE 420L Engineering Electronics II - Lab 6

Authored by David Flores

Due: March 27, 2019

Lab Description

In this lab we will be using the the ZVN3306A and ZVP3306A MOSFETs. This lab will show how the Mosfets operate in a few different examples. The examples consist of the Source Follower, Common Source Amplifier, Common Gate Amplifier, and Push Pull Amplifiers.

Pre-lab

This lab will utilize the ZVN3306A and ZVP3306A MOSFETs.
Review these datasheets and become familiar with these transistors.
Verify that the simulations seen in lab6_sims.zip reasonably model the behavior of the transistors' ID v. VGS, ID v. VDS, and gm v. VGS curves.
Finally, watch the video single_stage_amps and review single_stage_amps.pdf

Experiment 1: Common Drain Amplifier

Below are schematics for NMOS and PMOS source followers amplifiers (also known as common-drain amplifiers). In your lab report discuss the operation of these circuits.

Common Drain amplifiers also known as source followers, these circuits have a common source with the gates of the mosfets acting as the input and the drains of the mosfets acting as the outputs. In some cases, the common drain amplifiers are used as a voltage buffer. This will protect the input signal from the current drawn.

Hand calculate, and then verify your hand calculations with experimentation and simulations, the gains and the input and output resistances ensuring that your test signals are at a high enough frequency that the caps have negligible impedance but not so high that the gain is dropping off.

NMOS: PMOS:

Hand Calculations: Hand Calculations:

Simulate the operation of these amplifiers.

Spice Error Log .Op for Common Drain Circuit

LtSpice Simulations for both NMOS and PMOS Ltspice waveforms for Voutp, Voutn and Vin

Experimental Results:

VoutN: VoutP:

We can see that the gain is close to 1 for both Mosfets which matches the hand calculations above.

Nmos Input Resistance Pmos Input Resistance

Nmos Output Resistance Pmos Output Resistance

If you build this circuit using electrolitic capacitors, assuming the input AC signal swings around ground, put the "+" terminal of the cap on the gate of the MOSFET. Please indicate, in your lab report, that you understand why the capacitor is connected this way.

We built the circuits with electrolytic capacitors the reason for the orientation is because these capacitors are polarized which means that if we apply a negative voltage on the wrong side we could destroy the capacitor causing it to pop.

Measuring Input Resistance

For measuring the input resistance add a resistor equal to the value you calculated between the input voltage source and the amplifier. We added this resistor and then measured the voltages on both sides of the resistor to find the voltage drop and calculate the current through the resistor To find the input Resistance we finally we divide Vout by this current through the resistor to get our input Resistance

Measuring Output Resistance

For measuring output resistance, we added a resistor equal to the one calculated from the output to ground. We can then measure the output resistance using the voltage divider.

Experiment 2: Common Source Amplifier

Hand calculate the gains and the input/output resistances. How does the source resistance, Rsn or Rsp, influence the gain? Again, compare your hand calculations to simulation and experimental results.

NMOS: PMOS:

Hand Calculations: Hand Calculations: