Lab6

Lab 6 - EE420L

Dwayne K. Thomas

kendaleman@gmail.com

3/20/2015

Single-stage transistor amplifiers

Experiment 1: The common-drain amplifier

These are the simulation results of the amplifier

The common-drain amplifier is also known as the source follower amplifier. It is called common-drain because both the input and the output have the drain in common. It is called a source follower because the output of the amplifier is located at the source and follows the signal at the input. This amplifier configuration has a voltage gain close 1 which is calculated further below.

Amplifier circuits	NMOS circuit	PMOS circuit
Scope reading of the gain
Scope reading of the Input Resistance Test
Scope reading of the Output Resistance Test

In order to test the input and output resistance of the circuit, we connect a resistor in series that is the size of our caculated resistance and apply a test voltage. If our calculated resistance is correct, the resistor we place in series will have a voltage drop of half of our test voltage. If not, the equation on right helps us calculate the measured Resistance.

http://cmosedu.com/jbaker/courses/ee420L/s15/students/thomad1/Lab6/CalctestR.PNG

Below are the calculations for INput Resistance, OUTput Resistance and gain of the amplifier. We will use 18mV for the gm of the NMOS and 11mV for the gm of the PMOS. These are the values which also obtained in the .op simulation of our circuit. Although they are not exact due to the changing of gm. They will help us stay consistent with our calculations throughout our experiments.

http://cmosedu.com/jbaker/courses/ee420L/s15/students/thomad1/Lab6/1Calc_gain_rout_rin.PNG

Common-Drain amplifier Table	Calculated Gain	Measured Gain	Calculated input Resistance	Measured Input Resistance	Calculated Output Resistance	Measured Output Resistance
NMOS amplifier	0.947	1.2	33.33k ohm	26.4k ohms	52.63 ohms	58.5 ohms
PMOS amplifier	0.947	1.2	33.33k ohm	34.7k ohms	83.3 ohms	192 ohms

Experiment 2: The common-source amplifier

To the left is our simulation schematic and below are out simulation results

The common-source amplifier is called common-source because both the input and the output have the source in common. R1 and R3 create a voltage divider to bias the gate voltage on the NMOS. This is also accomplished by R4 and R5 in the PMOS circuit. The input is capacitively coupled on both circuits to maintain the biasing.

Amplifier circuits	NMOS circuit	PMOS circuit
Scope reading of the gain
Scope reading of the Input Resistance Test
Scope reading of the Output Resistance Test

Below are the calculations for INput Resistance, OUTput Resistance and gain of the amplifier. We will use 18mV for the gm of the NMOS and 11mV for the gm of the PMOS. We notice that increasing the Rsn or Rsp, decreases our gain.

Common-source amplifier Table	Calculated Gain	Measured Gain	Calculated input Resistance	Measured Input Resistance	Calculated Output Resistance	Measured Output Resistance
NMOS amplifier	-6.83	-5.2	33.33k ohm	26.4k ohm	1k ohm	724 ohm
PMOS amplifier	-5.4	-2.96	33.33k ohm	34.7k ohm	1k ohm	960 ohm

The large difference in gain of our PMOS can be due to gm that is very different from what we used to caculate

Experiment 3: The common-gate amplifier

These are the simulation results of the amplifier

Amplifier circuits

NMOS circuit

http://cmosedu.com/jbaker/courses/ee420L/s15/students/thomad1/Lab6/CommonGateNmosSchematic.PNG

PMOS circuit

http://cmosedu.com/jbaker/courses/ee420L/s15/students/thomad1/Lab6/CommonGatePmosSchematic.PNG

Scope reading of the gain

http://cmosedu.com/jbaker/courses/ee420L/s15/students/thomad1/Lab6/n_gain_comgate3.PNG

http://cmosedu.com/jbaker/courses/ee420L/s15/students/thomad1/Lab6/p_gain-comgate3.PNG

Scope reading of the Input Resistance Test

http://cmosedu.com/jbaker/courses/ee420L/s15/students/thomad1/Lab6/n_inputres3.PNG

http://cmosedu.com/jbaker/courses/ee420L/s15/students/thomad1/Lab6/p_inputres3.PNG

Scope reading of the Output Resistance Test

http://cmosedu.com/jbaker/courses/ee420L/s15/students/thomad1/Lab6/n_outputres3.PNG

http://cmosedu.com/jbaker/courses/ee420L/s15/students/thomad1/Lab6/p_output_res3.PNG

http://cmosedu.com/jbaker/courses/ee420L/s15/students/thomad1/Lab6/3calc.PNG

Common-gate amplifier Table	Calculated Gain	Measured Gain	Calculated input Resistance	Measured Input Resistance	Calculated Output Resistance	Measured Output Resistance
NMOS amplifier	6.55	5.28	152.6 ohm	418 ohm	1k ohm	980 ohm
PMOS amplifier	5.4	2.83	183.3 ohm	335 ohm	1k ohm	1.8k ohm

The large difference in gain of our PMOS can be due to gm that is very different from what we used to caculate

Experiment 4: The push-pull amplifier

http://cmosedu.com/jbaker/courses/ee420L/s15/students/thomad1/Lab6/PushPullamplifier.PNG

http://cmosedu.com/jbaker/courses/ee420L/s15/students/thomad1/Lab6/11pushpullsimplot.PNG

Above shows the PSPICE simulation results of the push-pull amplifier. The push pull amplifier allows the sourcing and sinking of current. The resistor allows for a constant DC voltage across the gate and sources of the transistors. No current flows through the resistor, it is used as a gain multiplier. Therefore as we increase the resistance from 100kohm to 510kohm, we esentially multiply the original gain by 5.

Hand Calculations

id = vsg1 * (gm1) id = vgs2 * (gm2)
because vsg = vgs = vin
Vout/Vin = (R1)*(gm1 +gm2)
Vout/Vin = 100k * (.011 + .018)
Vout/Vin = 2900

Using a 100kohm Resistor	Using a 510kohm Resistor

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