**Lab #3 – MOSFET Characteristics**

**Objectives:**

· To get acquainted with the characteristics of a typical MOSFET.

· To get practice designing the dc bias for a MOSFET to achieve the desired Q point.

**Procedures:**

1. Use the same setup we used to measure the JFET I-V
characteristics in Electronics I to obtain the I-V characteristics for either
the 2N7000 or the BS170 N-Channel MOSFET.
Carefully determine the threshold voltage at which drain current just
begins to flow. Save the I-V curves for
a number of values of V_{GS} and include a copy of these
characteristics in your report.

2. From the
characteristics determine the value of the transconductance gain g_{m }=
ΔI_{D}/ΔV_{GS}.
Compare your value with the data sheet for your transistor. Also, you should be able to calculate a value
for K_{n} for your transistor in the vicinity of the Q point (I_{D}@5mA
and V_{DS} @5V)

3. Compare the shape of the I-V characteristics with those for the 2N5458 JFET and comment on any differences you see. Also, compare the value of gm for your MOSFET with the JFET.

4. Design a dc bias circuit to meet these specifications (similar to problem 3.28).

I_{DQ} @5 mA

V_{DSQ} @5V

V_{DD} = 10V

V_{TN }= your measured
value

K_{n} = your computed value
from measurements

Voltage across R_{S} is
approximately equal to V_{GS}

5. Build the bias circuit that you designed using standard values of 5% resistors, and take measurements to determine how close you are to the above specifications.

6. Clearly present your findings for the MOSFET and discuss their meaning/application in your report.