EXPERIMENT8

Set up the following circuit on a bread board. Use a 470R for Rc and a BC547 NPN transistor.

Pick five resistors between 2K2 and 1M for Rb. You want a range of resistors that allow you to see Vce when the transistor is the saturated switch region and when it is in the active amplifier region. I used 2K2, 47K, 270K, 330K and 220K. 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= 0.73V, Vce= 26.3mV, Ib= 1.99mA, Ic= 6.5mA

Rb= 47k, Vbe= 0.68V, Vce= 1.10V, Ib= 0.11mA, Ic= 6.66mA

Rb= 270k, Vbe= 0.68V, Vce= 0.82V, Ib= 0.01mA, Ic= 4.44mA

Rb= 330k, Vbe= 0.67V, Vce= 1.41V, Ib= 0.01mA, Ic= 3.60mA

Rb= 220k, Vbe= 0.69V, Vce= 0.58V, Ib= 0.02mA, Ic= 5.30mA

EXPERIMENT7

Transistor as a switch.

1 x Small Signal NPN transistor, 2 resistors( R1=10K, R2=1K ).

Connect the multimeter between base and emitter.

Note the voltage reading and explain what this reading is indicating.

750mV. Becasue Vbe need to exceed 0.7 volts to operate and it is indicating that it is working correct.

Connect the multimeter between collector and emitter.

Note the voltage reading and explain what this reading is indicating.

52.4mV. This is indicating that the transistor is open, current flowing.

In the plot given below what are the regions indicated by the arrows A&B?

A indicates the saturation region and B indicates the cut off region.

How does a transistor work in these regions?

The saturated region means that the transistor is on and that it is a foward biased.

What is the power dissipated by the transistor at Vce of 3 volts?

Vce at 3 volts= (β= Ic /Ib) 12.5/0.5 β=25

What is the Beta of this transistor at Vce 2,3 & 4 volts?

β= Ic / Ib =

Vce 2 = 20/0.8=25

Vce 3 = 12.5/0.5=25
Vce 4 = 5/0.2=25

EXPERIMENT6

TRANSISTOR

A transistor is a semiconductor device used to amplify and switch electronic signals.

It is made of a solid piece of semiconductor material, with at least three terminals for connection to an external circuit.

A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals.

Because the controlled (output) power can be much more than the controlling (input) power, the transistor provides amplification of a signal.

Transistor Symbol and semiconductor construction

Identify the legs of your transistor with a multimeter.

EXPERIMENT5

CAPACITOR

The capacitor stores electric charge.



A capacitor consists of two metal plates very close together, separated by an insulator.

When connected to a battery or power source electrons flow into the negative plates and charge up the capacitor.

The charge remains there when the battery is removed. The charge stored depends on the “size” or capacitance of the capacitor, which is measured on Farads (F).

Types of Capacitor:
Non-electrolytic capacitor, Variable capacitor, Electrolytic capacitor, Tantalum capacitor.

Identifying Capacitor Size.

1 x resistor, 1 x capacitor, 1 x pushbutton N/O switch.

First, calculate how much time it would take to charge up the capacitor.

Then, connect the circuit as shown above. Measure the time taken by the capacitor to reach the applied voltage on an oscilloscope.

Fill in the chart below. Also draw the observed waveforms in the graphs below, filling the details on each one.

How does changes in the resistor affect the charging time?

Resistor affects the charging time. Higher value of resistor will take longer to charge than a lower value resistor

How does changes in the capacitor affect the charging time?

Bigger capacitor will take longer to charge.

EXPERIMENT4

Experiment 4

1 x resistors, 1 x 5V1 400mW Zener diode, 1X Diode1N4007.


Obtain a breadboard, suitable components from your tutor and build the following circuit.

Vs=10 & 15v, R=1K ohms
 
　　　　　　　　 　
 
 
                                     10 Volts　　　　　15 Volts

Volt drop V1:　　　　4.81v　　　　　　 4.93v
Volt drop V2:　　　　0.66v　　　　　　0.691v
Volt drop V3:　　　　5.47v　　　　　　 5.62v
Volt Drop V4:　　　   4.44v　　　　　　 9.4v
Calculated current A:  10㎃　　　　　　　15㎃

Describe what is happening and why you are getting these readings:
 
Current reduces while flowing through the resistor and diodes.

EXPERIMENT3

Zener Diode.

 

A Zener diode is a type of diode that permits current not only in the forward direction like a normal diode, but also in the reverse direction if the voltage is larger than the breakdown voltage


 
 

 

2 x resistors, 1 x 5V1 400mW Zener diode (ZD).

For R= 100ohm and RL= 100ohm, Vs= 12 V.

What is the value of Vz?

5.02V

Vary Vs from 10V to 15V

What is the value of Vz?
5.08V

Explain what is happening here
The circuit is regulating the voltage.

What could this circuit be used for?
Voltage regulator.

Reverse the polarity of the zener diode.

What is the value of Vz? Make a short comment why you had that reading.

836mV. Reversed zener diode reduces current flowing through it but a small amount of current still flows.

EXPERIMENT2

Diodes

A diode has the characteristics of:

• An insulator when current tries to flow in one direction.

• A conductor when current flows in the other direction.

 

 

 

 

 

Exercise: Using a multimeter, identify the anode and cathode of the diode and the LED.

                                                                     LED                    Diode

Voltage drop in foward biased direction:        2.4v                  681mV

Voltage drop in reverse biased direction:       OL                      OL

Explain how you could identify the cathode without a multimeter:

The cathode end is marked with a white line and the short leg is for the LED.

                             Vs=5v, R=1k, D=1N4007

Calculate first the value of current flowing through the diode, now measure and check your answer.

Calculated: 5/1000= 0.005= 5mA Measured: 50mA

Calculate the voltage drop across the diode.
Calculated: 700mV Measured: 683mA


Replace the diode by an LED & calculate the current, then measure and check your answer.
Calculated: 1.8A Measured: 3.18mA

EXPERIMENT1

Resistors

Resistors reduce and limits the current. A thin film of carbon is deposited onto a small ceramic rod. Resistor is covered with an insulating coating and painted with colour bands to indicate the resistor value.


Identifying, Testing and Combining Resistors




• First two or three bandsmay be the numbers towrite down

• Next band is the multiplier(how many zeros to add tothe number)

• Gold multiplier makes onedecimal place smaller,Silver makes two decimalplaces smaller

• Last band to right may betolerance values

• Notice the examples on theright

• Brown, red, red = 1, 2, 100,5% = 1200 5%, or1.2K ,1K2




Obtain 6 resistors of different values.

Recorded values in the chart:
(Colour Codes)　(Multimeter)
2200 ± 5% Ω　　 2.16kΩ 　(Red, Red, Red, Gold) 2090~2310Ω
47000 ± 5% Ω　　46.1k Ω 　(Yellow, Violet, Orange, Gold) 44650~49350Ω
100 ± 5% Ω　　　99.6k Ω 　(Brown, Red, Gold) 95~105Ω
22000 ± 5% Ω　　221k Ω 　(Red, Red, Yellow, Gold) 20900~23100Ω
10000 ± 5% Ω　　9.82k Ω　 (Brown, Black, Orange, Gold) 9500~11500Ω
27000 ± 5% Ω　　270k Ω 　(Red, Violet, Gold) 25650~28350Ω

Two resistors ohm resistance value measured with a multi-meter.

Resistor 1 : 2.16k Ω
Resistor 2 : 46.1k Ω

Two resistors calculated and mesured value, put together in series.

a)Calculated value 1 and 2 in series: 49200 Ω
　Measured value 1 and 2 in series: 48.2k Ω

b)Calculated vlaue 1 and 2 in parallel: 2.10k Ω 　
　Measured vlaue 1 and 2 in parallel: 2.07k Ω

Measured using:
R1 x R2　2.2k x 47k
--------- = --------------- = 2.1k
R1 + R2　2.2k + 47k