Experiment No.8 - Transistor Voltage drop

In this experiment we where to create a circuit and vary the base resistor and measure changes in voltage and current for Vce, Vbe, Ic and Ib. Then plot a load line.

I used a 470R for Rc and a BC547 NPN transistor

these are the reading I found

Vce is the voltade between the collector and emitter, You can see in the table as the Rb increases the Vce also increases. This shows that wih a higher resistor and less voltage getting to the base there is going to be a greater voltage drop.

The vbe is the voltage between the base and the emitter, as shown in the table there is very little change between the vbe . This is becasue the transistor only requires 0.7v to operate.

the higher the Rb the lower the Lb is going to be,this is because there is such a large resistance there is going to be less current at the base.

The Ic was lower as the resistance increased. The greater the Ic the more the transistor is on which is increased current flow.

Here is the graph which i plotted the table onto.

Beta = Vce at 1.25v = 5.9mA and 70MA

B = 0.0059 / 0.000070 = 84.2

The load line on the graph is showing the relationship of Ic and Vce. This load line on this graph is showing the transistor is saturated at 8.27mA at .7 volts and cuts off at 113.9MA.

Experiment No.7 - Transistor as a switch

In this Experiment I had to make a circuit and use a transistor as a switch and run some tests on it using a multimeter.

Vbe = .74v

This shows that the transistor has a knee voltage of .74 volts

Vce = 0.05v

There is only a voltage drop of 0.05v, this shows that the current is flowing through the transistor freely.

In this graph, in region A the transistor is in the "fully on" position and in region B it is in the "fully closed" posistion.

Power dissapating at a Vce of 3v,

Vce = 3 Ic = 14

Ic * Vce = Pd

14 * 3 = 42mW

Beta at at Vce of 2,3 & 4 volts

Vce2 = 20 / 0.8 = 25mA

Vce3 = 14 / 0.5 = 28mA

Vce4 = 5 / 0.2 = 25mA

Experiment No. 6 - meter check of a transistor

In this experiment I had to identify the legs of my transistor with a multimeter, I was able to refer to the representations to identify and test the transistors.

The multimeter was used to measure voltage drop between the legs, I tested them in NPN and PNP.

Experiment No. 5 - Capacitors

In this experiment I had to caculate how long it would take to charge 4 different capacitors then observe them charging on a scope.

First there was a circuit I had to put together which would be used to observe the time taken to charge the capacitors.

These are the results I got by using a simple formula - R x C x 5 = T, this is the time it takes to charge up to the applied voltage.

These are the images taken from the graph on the scope using the different capacitors and resistors.

100uF , 1Kohm 100uF , 0.1Kohm

330uF , 1Kohm 100uF , 0.47Kohm


Changes in the resistor affect the charging time by the larger the resistor the lower the current flow is going to be as it is restriced and if it is a smaller resistor more current flow will be able to pass so it will take less time to charge.

Changes in the capacitor affect the charging time because the larger the capacitor the longer it will take to charge as it can hold more charge ans with a smaller capacitor it hold less charge so it will take less time to charge.