EGRE 306 – Introduction to Microelectronics

Using Multisim, you will first measure the I-V characteristics of an n-channel MOSFET so that you can predict the transistor’s behavior. Then, you will take data to use the transistor as a voltage-controlled resistor.

Set-Up

To measure the threshold voltage, you will apply a large V_DS voltage (10V) and slowly increase the gate voltage until you obtain a current. Remember that if V_GS < V_t, then the transistor will be in the cutoff region and “no” current will flow.

Continue to increase V_GS and measure and plot the I_D vs. V_GS graph for your transistor. Your resulting graph should resemble the figure below. Do not exceed 200mA.

Now, you will take data to help you calibrate your voltage-controlled resistor.

1. Set v_DS to a small value (~50mV).

I_D = 0.4mA at V_GS=4V

v_DS = 0.1V I_D = 0.5mA at V_GS=3V

For V_GS = 4V The drain current increased 0.7mA when the drain voltage

increased by 0.05V. The channel resistance at V_GS = 4V is:

Using your results, determine the MOSFET transconductance value (k_n) for your transistor (calculate it for each of your ten data points).

5. Determine the correct bias conditions (V_GS) so that your transistor has a resistance of 110 Ohms.

Part II Data

k_n = ____________

EGRE 306 – Introduction to Microelectronics

Part II - DC Biasing of MOSFET

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1. Connect two separate power supplies to the Drain and Gate of your MOSFET. Apply a large V_DS voltage (5V).

2. Connect the Source to ground and use the ammeter to measure the drain current (between the V_DD source and the drain of the transistor).

Using the data from steps 3, 4, 5, 6 and

I_D = 0.5 k_n (V_GS1 – V_t)² 4I_D = 0.5 k_n (V_GS2 – V_t)²

V_t = ________________ k_n = ________________

Q1: For all of these measurements, what region of operation is the transistor operating in?

2. Find (calculate) R_G1 and R_D so that there will be a drain

current of ~20mA and V_DS ~V_DD/2

Analysis Hints:

1. Assume the transistor is operating in the saturation region.

Part III – Another DC Biasing Circuit for MOSFET

1. Build the circuit on the right, using your

measure V_D, V_S, and I_D.

Analysis Hints:

Q3: What are pros/cons of this biasing circuit?

Lab Report (Individually done, One per PERSON)

1. Cover Page (As seen on previous templates, include: name, class, title, section, date, partner (if you have one), honor pledge - signed, etc.)

2. Introduction to the lab: Explain what the purpose of this lab was and a brief description of the purpose for each part of the lab you completed (max of 2 paragraphs).

5. Conclusion: This is where you write a summary of the experiment, including answers to all of the questions that were included in the lab handout.

To Be Included:

determined the threshold voltage and MOSFET transconductance parameters for your transistor. (This will be a lengthy answer)

3. Schematic diagram of your Part II circuit (using Multisim). Include voltmeter/ammeter

items that you should include in the appropriate areas are:

• Description of HOW you determined Vt for your transistor.

voltmeter/ammeter where you measured voltage and current.

7. Part III calculations, showing how you determined R_S and R_G1 that satisfy the given