SIDNEY HYUGA

ENE 211-0294/2020 B1
Electrical and Electronics Engineering

Jomo Kenyatta University of Agriculture and Technology

Department of Electrical and Electronics Engineering
PHYSICAL ELECTRONICS
EEE 2212
MOSFET AND BJT SIMULATION REPORT
Laboratory Exercise
PREPARATION
1. Search the internet for the datasheet for the 2N7000 N-Channel Enhancement MOSFET. Using
the datasheet, identify the value of following parameters for the transistor and explain the
meaning of each parameter:

(a) Drain –Source Breakdown Voltage; = 60 v -This is the maximum voltage that can be applied
between the drain and source terminals without causing damage to it

(b) Threshold voltage; = 1.1v-2.3v / (1.8V)-This is the voltage greater than the barrier potential that
is required to be reached before a PN junction can conduct.

(c) RDS(ON) ; =5 ohms

Turn ON time =5ns

Turn OFF time =7ns

2. Search the internet for the datasheet for the 2N2222 BJT. Identify the Identify the value of
following parameters for the transistor and explain the meaning of each parameter (where
multiple values exist, select typical value (if available), VCE = 10V and normal ambient
temperature):

a.) VCBO =60V This is the collector-base voltage at which a specified collector-base current flows
when the emitter terminal is open.

b. _VCEO =30V This is the collector emitter saturation voltage drop that occurs when the transistor is
carrying current.

c.) Maximum Power Dissipation =600mW This is the power dissipated in the transistor when the
voltage drop across the collector-emitter junction is multiplied by the collector current.

d.) DC β - This is the ratio of the transistor’s collector current (Ic) against its’s base current (Ib).

e.) tr -(Rise time) =25ns This is the time taken for the collector current to reach from 10% of its initial
value to 90% of its final value.

f.) td-(Time delay) =10ns This is the time taken by the collector to reach from its initial value to 10%
of its final value.

g.) ts -(Storage time) =225ns This is the time interval between the trailing edge of the input pulse to
90% of the maximum value of the output.

h.) tf-(Fall time) =60ns This is the time taken for the collector to reach from90% of its maximum
value to 10% of its initial value

3. How do the switching times for MOSFET in (1) compare with those for the BJT in (2)? Which
operating factors for the BJT contribute to the observed differences? A BJT has faster switching
speed as compared to MOSFET. This is because MOSFET has input capacitance, gate charge, output
capacitance and a higher delay, rise and fall time which make it slightly slower than a BJT during
switching where as a BJT does not have these parameters or are negligible making a BJT faster than a
MOSFET.
7.

Figure 3(c) shows an LED driven by a transistor. The LED has a forward voltage drop of 1.5V and
the transistor has β = 150. If required, it can be assumed that in ACTIVE region, VBE = 0.7V and in
SATURATION region, VCE = 0.2V.

a. Why is the forward voltage drop of the LED higher than that of a silicon P-N diode?

b. If VCC = VBB = 5 volts, RC = 4.7kΩ and RB = 220Ω.

i. Determine the operating region of the BJT.

ii. Determine the current in the LED.

iii. Determine the current in the LED if the BJT is replaced by a similar one but with β = 75
JKUAT: EEE 2212 Laboratory Exercise
PRACTICAL EXERCISES
Objective
The objective of this laboratory exercise is to:

1. Introduce the student to circuit simulation.

2. Apply circuit simulation to carry out the following exercises on an N-Channel Enhancement
MOSFET:

a. Derive the device parameters: threshold voltage, Vth and transconductance parameter, 𝐾𝑛(= 𝑊
2𝐿 μn𝐶𝑜𝑥).

b. Plot the transfer and output characteristics in common source configuration.

c. Use the characteristics to derive the small signal equivalent circuit parameters for the MOSFET.

2. Demonstration the operation of MOSFET and BJT as a switch, measure and compare the
switching times.

Equipment
Computer installed with circuit design and simulation software based on SPICE e.g. NI Circuit Design
Suite (Multisim). The descriptions in this document are based on NI Circuit Design Suite (Multisim).

EXERCISE 2: MOSFET Characteristics

Exercise 2(a) Transfer characteristics

Exercise 2(b) Output Characteristics

RESULT ANALYSIS 2(B)

1. Does the MOSFET have input characteristics? Explain. YES. Though the gate current is zero since
the gate terminal is electronically isolated from the other terminals the transfer characteristics is
used to relate the drain current (Id) in response to the input gate-source driving voltage (Vgs).

2. The input characteristics show the same drain current for the three values of VDS at low values
of VGS. Why do the curves separate at high values of VGS? This is because as the input gate-source
voltage (Vgs) increases the Threshold voltage is reached where the drain current begins increasing
indicating a decrease in the equivalent resistance.

3. On each of the output characteristic curves, plot the point at which VDS = VGS – Vth. Plot a
graph to join the points. What does it signify?
Exercise 3: MOSFET and BJT Switching Transients
Exercise 3(a): MOSFET Switch
Exercise 3(b): BJT Switch
Result Analysis
1.For the MOSFET:

a. Estimate the Turn ON time and Turn OFF time.

b. How does it compare with the value from the datasheet?

2. For the BJT Exercise 3(b):

a. Estimate the Turn ON time and Turn OFF time.

b. How does it compare with the value from the datasheet?

c. How does the turn off time compare with that of the MOSFET?

References
1. V. C. Gaudet, K. C. Smith, laboratory Explorations for Microelectronic Circuits Fourth Edition, New
York: Oxford University Press, 2004.

2. A. S. Sedra, K. C. Smith, T. C. Carusone, V. Gaudet, Microelectronic Circuits, 8 th Ed., New York:

Oxford University Press, 2020.

3. National Instruments, Electronics WorkbenchTM: MultisimTM 8 Simulation and Capture: User

Guide, Austin, Texas, NI, 2005

4. Labcenter Electronics Ltd, Proteus Design Suite: Getting Started Guide, 2019

5. J. M. Fiore, Semiconductor Devices: Theory and Application - Laboratory Manual, Self-Published,

Utica, NY, 2019

6. Philips Semiconductors, 2N7000: N-channel enhancement mode vertical D-MOS transistor,

Eindhoven, The Netherlands, Philips Electronics, 1997.

7. Semiconductor Components Industries (ON Semiconductors), PN2222: General Purpose

Transistor, Aurora, Colorado, 2018.