Experiment #8 Common Emitter

Pick five resistors between 2K2 and 1M for Rb. You want a range of resistors that allow you to see Vce when the trnsistor is the saturated switch region and when it is in the active amplifier region. I used 47K, 220k, 330k and 1M, but this can vary depending on your transistor. Some may need to use 2k2. Put one resisitor in place, and measure and record voltage drop across Vce and Vbe. Also measure and record the current for Ic and Ib. Then change the Rb resistor and do all the measurements and record the new readings. Do this for each of the resistor values above.

Rb: 2K2
Vbe: .778V
Vce: 26.5mV
Ib: 1.94mA
Ic: 6.19mA

Rb: 10KR
Vbe: .738V
Vce: 45.5mV
Ib: 0.42mA
Ic: 6.15mA

Rb: 47KR
Vbe: .709V
Vce: 90.5mV
Ib: 90uA
Ic: 6.06mA

Rb: 220KR
Vbe: .684V
Vce: .525V
Ib: 19.4uA
Ic: 5.29mA

Rb: 270KR
Vbe: .678V
Vce: .921V
Ib: 16.4uA
Ic: 4.49mA

Discuss what happened for Vce during this experiment. What change took place, and what caused the change?
: As resistance is increased the voltage for Vce increases.

Discuss what happened for Vbe during this experiment. What change took place if any, and what caused this change?
: Because the transistor is fully on with each resistor Vbe will be close to or around 0.7V as was shown by the results.

Discuss what happened for Ib during this experiment. What change took place, and what caused the change?
: As resistance increases Ib gradually gets smaller and smaller to the point where it gets into uA's.

Discuss what happened for Ic during this experiment. What change took place, and what caused the change?
: As with Ib, the more resistance that is added to the circuit the less current that will be sent to the collector.

Experiment #7 Transistor Switch

Connect the multimeter between the base and emitter.
Note the voltage reading and explain what this reading is indicating.
: 0.730V, this indicates a saturated transistor that is fully on.

Connect the multimeter between collector and emitter.
Note the voltage reading and explain what this reading is indicating.
: 50mV, this indicates again a saturated transistor as Vce will be very close to 0V when fully on.



A = Saturated (fully on)
B= Cut-Off (fully off)

How does a transistor work in these regions? Explain in detail:
When fully Saturated Vce will be very small but be putting out a high current.
When fully Cut-Off Vce will be small or large but be putting out very small current because the transistor becomes reverse biased.

What is the power dissipated by the transistor at Vce of 3V?
: Pd = Vce x Ic
3V x 12.5mA
37.5V Correction: 37.5W

What is the Beta of this transistor at Vce 2, 3, & 4 volts?
: B = Ib / Ic

2V: 20mA / 0.8mA = 25
3V: 12.5mA / 0.5mA = 25
4V: 5mA / 0.2mA = 25

This is because the beta will always be the same as it is taken off the gradient line you see in the graph.

Experiment #6 Meter Check

Identify the legs of your transistor with your multimeter.
In order to do this I used the diode test function of my multimeter by switching it to the point where a picture of a diode is displayed.

NPN

Vbe: .532V
Veb: OL
Vbc: .541V
Vcb: OL
Vce: OL
Vec: OL

PNP

Vbe: .583V
Veb: OL
Vbc: .587V
Vcb: OL
Vce: OL
Vec: OL

Experiment #5 The Capacitor

T = R x C x 5

Calculated Times:

0.0001 x 1000 x 5 = 0.5s or 500ms

0.0001 x 100 x 5 = 0.05s or 50ms

0.0001 x 470 x 5 = 0.235s or 235ms

0.0003 x 1000 x 5 = 1.5s

27/10/10 Correction for 330uF: 0.000330 x 1000 x 5 = 1.650s or 1650ms

Observed Times: 1: 0.5s
2: 0.2s
3: 0.3s
4: 1.8s

How does changes in the resistor affect the charging time?: As resistance increases the time taken to reach maximum charge increases also.

How does changes in the capacitor affect the charging time?: Like increased resistance, the larger capacitor will take longer to charge and also because of the larger capacity will take longer to discharge

Experiment #4 Zener Circuit 2

Explain what is happening here and why: The Voltage for V1 and V3 is at or around 5V because the Zener diode is acting as a 5V regulator. V2 is reading as it should as the diode will drop 0.7V.
V4 is highest at 15V because its coming in before the diode and so takes the most of the voltage.

27/10/10 Correction for V4: Increasing the voltage will therefore increase the resistance at V4 resulting in a higher voltage being read at the resistor.

Experiment #3 Zener Circuit

For R=100 ohms and RL=100 ohms, Vs=12V

What is the value of Vz?: 4.98V

Vary Vs from 10V to 15V
What is the value of Vz?: 4.74V - 5.06V

Explain what is happening here: At all stages of voltage, Vz stays at around 5V because the Zener is regulating the voltage to a maximum of 5.1V

What could this be used for?: As i stated above this circuit would be used as a voltage regulator.

Reverse the polarity of the Zener Diode
What is the value of Vz? Make a short comment why: .863V, this has happened because the Zener in reverse bias becomes like a regular foward bias diode.

Experiment #1 Resistors

Obtain 6 Resistors of different values. You are then going to determine their value two ways: use the colour code, Include the maximum and minimum tolerance value of each resistor then measure the resistor value with an ohmmeter.
Record your values in a chart

Choose 2 resistors and record their individual ohm resistance value measured with an ohmmeter.
R1: 996K ohm
R2: 468K ohm

Calculated Series: 1464K ohm
Measured Series: 1461K ohm

Calculated Parallel: 318.4K ohm
Measured Parallel: 319.6K ohm

What principles of electricity have you demonstrated with this? Explain.

With these readings and calculations I have shown the principles of resistors in a circuit.
When connected in series, 2 resistors are added together to get a total resistance.
When connected in parallel, total resistance of 2 resistors is given by the formula Rt = R1xR2/R1+R2