EE 420L Engineering Electronics II Lab - Lab 6
Single-stage transistor amplifiers

Authored by Sergio Covarrubias

covars1@unlv.nevada.edu

03/20/2016

• 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 Source Follower

• 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.
  
• Simulate the operation of these amplifiers.
• 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.
• 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.
  
• In your lab report discuss, in your own words, how to measure the input resistance.
• For measuring the input resistance add a resistor equal to the value you calculated between the input voltage source and the amplifier.
• Measure the peak AC current through this added resistor by taking the difference in the peak AC voltages across the resistor (on one side is the input voltage signal and the other side is the connection to the amplifier's input capacitor) and then dividing by the resistor's value.
• Measure the peak AC voltage on the input of the amplifier (the left side of the capacitor).
• Dividing this peak AC voltage by the peak AC current through the added resistor is the amplifier's input resistance.
• Again, in your lab report discuss how to measure the output resistance.
• For measuring the output resistance, add a resistor equal to the value you calculated in series with a big capacitor (to avoid messing up the biasing) from the amplifiers output to ground. 
• Measure the peak AC current through this added resistor.
• Measure the peak AC voltage (remove the DC component) on the gate of MOSFET and the peak AC voltage on the source of the MOSFET. The difference in these two AC voltages is the peak AC gate-source voltage of the MOSFET.
• Dividing this peak AC gate-source voltage by the peak AC current through the added resistor is the amplifier's output resistance.

(Vin-id*R2)*gm=id 

id*R2=Vout(R6)

Av=R2/(1/gm+R2)

NMOS
The Gain is: Measured Av=Vout/Vin=0.92 gm=1/(R2/Av-R2)=11.82mA/v
The estimated Input Resistance is: Rin=(R1||R3)=33.333K The measured Rin=(3.33k/V1/V2-1)=34.5K
Output Resistance: Rout-estimated=R2||(1/gm)=100 Rout-measured=100/(V1/V2-1)=137

PMOS
The Gain is: Measured Av=Vout/Vin=0.81 gm=1/(R6/Av-R6)=4.0mA/v
The estimated Input Resistance is: Rin=(R4||R5)=33.333K The measured Rin=(3.33k/(V1/V2-1))=55K
Output Resistance: Rout-estimated=R6||(1/gm)=100 Rout-measured=100/(V1/V2-1)=191

Experiment #2 Common Source

• Below are two common-source amplifiers.
• Discuss the operation of these amplifiers in your lab report including both DC and AC operation. 
• 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
The Gain is: Measured Av=Vout/Vin=5.3 gm=1/(R8/Av-RSN)=11.82mA/v
The estimated Input Resistance is: Rin=(R1||R3)=33.333K The measured Rin=(3.33k/(V1/V2-1))=32K
Output Resistance: Rout-estimated=R8||(1/(gm+RSN))=950 Rout-measured=100/(V1/V2-1)=821

PMOS
The Gain is: Measured Av=Vout/Vin=3.5 gm=1/(R7/Av-RSP)=4.6mA/v
The estimated Input Resistance is: Rin=(R4||R5)=33.333K The measured Rin=(3.33k/(V1/V2-1))=40K
Output Resistance: Rout-estimated=R8||(1/(gm+RSN)||R2)=950 Rout-measured=100/(V1/V2-1)=933

Experiment #3 Common Gate Amplifier

• Below are two common-gate amplifiers.
• Discuss the operation of these amplifiers in your lab report including both DC and AC operation. 
• 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
The Gain is: Measured Av=Vout/Vin=4.7 gm=(Av)[(RSN+R2)/(R2*R8)]=5.51mA/v
The estimated Input Resistance is: Rin=(R2+RSN)||(1/(R8+gm))=200 The measured Rin=(200/(V1/V2-1))=30K
Output Resistance: Rout-estimated=R8||(1/(gm+RSN)||R2)=1K Rout-measured=1K/(V1/V2-1)=971

PMOS
The Gain is: Measured Av=Vout/Vin=2.5 gm=(Av)*[(RSN+R6)/(R6*R7)]=3.00mA/v
The estimated Input Resistance is: Rin=((RSN+R2)||(1/(R8+gm)))=330 The measured Rin=(330/(V1/V2-1))=32K
Output Resistance: Rout-estimated=R8||(1/(gm+RSN)||R2)=1K Rout-measured=100/(V1/V2-1)=987

Experiment #4 Push-Pull Amplifier

• Below is a push-pull amplifier.
• Discuss the operation of this amplifier in your lab report including both DC and AC operation. 
• Hand calculate the gain of this amplifier.
• Do you expect this amplifier to be good at sourcing/sinking current? Why or why not?
• What happens to the gain if the 100k resistor is replaced with a 510k resistor? Why?
  
• Again compare your hand calculations to simulation and experimental results.
• Note that the gain of this amplifier is large so the output may saturate at VDD and Ground. To avoid this saturation you can reduce the AC input voltage using a voltage divider.

NMOS
Using the 100K resitor we get: Using calculations. Av=R1*(gmN+gmP)=1.6KV/V Measured: Av=511*(Vout/Vin)=756KV/V
Using the 510K resitor we get: Using calculations. Av=R1*(gmN+gmP)=8KV/V Measured: Av=511*(Vout/Vin)=1.1KV/V