• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Transistors in Switch and Amplifier Configurations.

Extracts from this document...



Transistors in Switch and Amplifier Configurations


Transistors are electronic devices usually used as amplifiers or oscillators in communications and computer systems. They consist of a tiny piece of semiconducting material, usually silicon or germanium, to which three or more electrical connections are made. The basic components of the transistor are similar to those of a triode vacuum tube and include an emitter, which corresponds to the heated cathode of the triode tube as the source of electrons. The transistor was developed by American physicists John Bardeen, Walter Houser Brattain and William Bradford Shockley.

This assignment requires us to carry out a number of tasks. For the first stage of the assignment, I will be performing four tests relating to the BC147 transistor to determine its characteristics. Graphs will be plotted with the results gained from this. Then I will carry out an experiment relating to a transistor switch circuit, answering a few questions relating to the experiment.

        Another experiment will be performed for the third part of the assignment, this time relating to the common emitter amplifier.

...read more.



IB = IC / HFE = 0.069 / 96 = 7.19 x 10-4A

R = (VCC – VBE) / IB

R = (12 – 0.74) / 7.19 x 10-4 = 15666Ω

RB(a) = 15666 – 1000 – 10000 = 4666Ω

        Since RB(a),(b),(c) are known values, the calculation will reflect this before your final choice for RB is made.

        Now complete the following tests:

TEST 1: Adjust the potentiometer (RB(c)) to achieve the calculation as  measured on an ohmmeter. Apply the power supply and record the readings of the various meters. If VCE (sat) (or a lower value) can’t be achieved, is RB(a) to high a value?

IC (sat) = 68.1mA

IB (sat) = 0.705mA

VCE (sat) = 0.74v

VBE (sat) = 0.24v

TEST 2: State the practical value of HFE using the recorded test figures. State the percentage error between this and the original value of HFE.


HFE = 68.1 / 0.705 = 96.6

% Error = (Calculated HFE / Measured HFE) x 100%

% Error = (96.6 / 96) x 100%

% Error = 100.625 – 100 = 0.625%

TEST 3: Determine the maximum value that VCE may rise to, before there is a significant fall in the collector current.

VCE = 1.90v

QUESTION 1: When RB(c) was adjusted, at what point would a power rating for the transistor need consideration.

More current flows as the voltage is decreased. Therefore, the lamp will brighten.

...read more.


order:0px solid #000000;width:1.33px;height:37.33px;">image22.png















  1. Unijunction Transistor (UJT)









This is one of the simplest oscillator circuits based on a unijunction transistor. In the above circuit, the potential difference across the capacitor gradually builds up and is released almost instantly. This type of oscillator is known as a ‘relaxation oscillator’.

...read more.

This student written piece of work is one of many that can be found in our AS and A Level Electrical & Thermal Physics section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Electrical & Thermal Physics essays

  1. Peer reviewed

    Test of the reed switch capacitors in series and in parallel

    3 star(s)

    V = 4.55V Measured current I = 0.4mA Therefore, theoretical current I = CVf = (0.22x10-6)(4.55)(400) = 0.4004mA Capacitors in series The results were recorded as shown as below: Capacitance C1 = 0.22�F Capacitance C2 = 0.22�F Equivalent capacitance Ceq = (1/ 0.22 x10-6+1/ 0.22 x10-6)-1 = 0.11�F Frequency f = 400Hz P.d.

  2. Objective: l To rectify ...

    Use the CRO to confirm that the selected output of the low voltage power supply is an a.c. If so, measure its peak voltage v1 and frequency f1. 3. Use the CRO to display the signal across the resistor.

  1. The objective of this lab was to experiment with a negative feedback amplifier and ...

    The applications of this are discussed in the individual discussion section. Table 2: Feedback circuit values (step 1) AV 100 v/v RFEEDBACK2 16.32k? fH 940KHz Table 3: Non-Feedback circuit values (step 2) VI .01 V VO 15.09 V AV 1509 V/V RFEEDBACK2 INFINITY fH 185KHz Grant's Discussion This time around

  2. AC Generator

    I found out that the more rotations per minute the higher the voltage, therefore the faster the velocity of relative motion between the coil and the magnets, the greater the current produced as stated in my expected results. Also from the formula...

  1. Operational amplifiers (opamps)

    A basic opamp with negative feedback is shown below in figure 2. Figure 2: A basic opamp with positive feedback Contrary to opamps with negative feedback, opamps with positive feedback have non-linear input-output relationships. The output voltage will always be either the maximum or minimum voltage possible.

  2. Current rating of fuses and MCB's.

    the reason that it has replaced the fuse in most domestic applications, these being reusability, reliability and added safety. Since there is a trip, the MCB can be used simply by tripping it back on. Also they have better response times and are also far more reliable.

  1. Practical Project (2863/02): The Characteristics of a Shunt Wound Motor

    The angular velocity can be measured by using a stroboscope, which determines how many turns the motor makes per second. Method of Choice I have chosen to use Method 2, because it is much more practical to carry out, in that I don't need to go and find a tall building and mark the wall all the way up.

  2. To find which of the circuits, shown below, are most suitable to measure a ...

    to the specification mentioned on the first page on my planning: Maximum Pd 5V, Maximum Current 100�A Until the actual experiment commences, I will not know for sure how accurate this device is but I will ensure that I pick the most accurate equipment that I have at my disposal.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work