Electronic

Diagram (4.1) shows a bright spot, P, formed on the screen of a cathode-ray oscilloscope, C.R.O. when it is switched on. What is the meaning of cathode ray? [1 mark] Explain how the bright spot is formed on the screen of the C.R.O. [2marks] Diagram (4.2) shows the bright spot is displaced to (Q) when … Read more

Logic gates can be combined together to perform certain tasks. The output can be determined by constructing a truth table. Example 1: In the combination of logic gates above, find the outputs X, Y and Z of the inputs A and B.Answer: INPUT OUTPUT A B X Y Z 0 0 1 1 1 0 … Read more

Symbol of the Logic Gate For each gate, the input or inputs are on the left of the symbol. The output is on the right The Truth Tables The function of a logic gate can be shown by using the Truth tables. A truth table lists all possible input together with the corresponding output. AND … Read more

A logic gate is a physical device that performs a logical operation on one or more logical inputs and produces only one logical output. The input is the signal or data that fed into a logic gate whereas the output is the result of processing the inputs by using the operation of the logic gate. … Read more

The Transistor as an Automatic Switch A transistor can be used as automatic switches. In the diagram above, the bulb is off when the collector current is off or very small. It is switched on when the collector current becomes large.  We have learned that in a transistor, the collector current is controlled by the … Read more

Transistor as an Amplifier The major application of a transistor is as a current amplifier. A transistor can be used to amplify (‘magnify’) current changes because a small change in base current produces a large change in collector current. A simple transistor amplifier circuit is shown in Figure 1 below. (Figure 1) The graph in … Read more

Current in a Transistor The current flows in the base, emitter and collector are called the base current (IB), the emitter current(IE) and the collector current(IC) respectively. The figure below shows the direction of the current in an npn transistor. In general, IE is related to IB and IC through the formula IE = IB … Read more

Connection of Transistor The terminals of a transistor must be connected to the terminals of a cell correctly to avoid damaging the transistor. Transistor should be connected in such a way that the emitter-base circuit is forward bias the collector-base circuit is reverse bias. Example: Emitter-Base: Forward Bias Collector-Base: Reverse Bias Connection: CORRECT Example: Emitter-Base: … Read more

Transistors A transistor is a double p-n junction semiconductor with three terminals,  the emitter (e),  the base (b)  the collector (c). Figure 1 below shows the illustration of a transistor. It looks like a combination of 2 p-n junction diodes. (Figure 1) In a transistor, the emitter emits charge carriers (free electrons or holes). The charge carriers … Read more