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 A transistor is the basic building block of electronic components.  The average computer may have millions of them within its circuits.  Essentially,

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Presentation on theme: " A transistor is the basic building block of electronic components.  The average computer may have millions of them within its circuits.  Essentially,"— Presentation transcript:

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3  A transistor is the basic building block of electronic components.  The average computer may have millions of them within its circuits.  Essentially, it is an electronic switch.  This is the symbol for an NPN transistor

4  The three terminals are called the Base, Collector and Emitter.  When the “switch” is ON, a large current will be allowed to flow through C to B and out of E  For this to happen, a current must first flow through B (from the left). B C E Current out = Current in + Current in at E at B at C I e = I b + I c

5 A simple light operated switch. When the base voltage is high enough, the current through it will “open the gate” and allow a very large current to flow through the bulb so that it lights. 1.This will happen when the voltage across the LDR is high. 2.So the resistance of the LDR must be high for the light to be ON. 3.The resistance of the LDR is high in the dark. 4.So the light will come on when it gets dark!

6 ABOutput High ON HighLowOFF LowHighOFF Low OFF If two transistors are connected as shown to make a switch… A current will flow when it is ON This can only happen if a current flows into A AND B If the current into either input A or B drops, then the switch will be OFF This table shows the combinations of inputs and the outputs produced

7 What are logic gates? What are logic gates? Logic gates are electronic switches that process information. This chip contains four NOT gates. They are called gates because they open to produce a high output signal only when they receive the correct combination of input signals. A large number of logic gates can be incorporated in one electronic chip. Most logic gates have multiple inputs, which are used to determine a single output.

8 Microchips contain logic gates, which use this binary code to send and store information. Digital systems have two states, ON and OFF. These simple electronic states are represented in binary code: ON is called logic 1; OFF is called logic 0. Logic gates receive multiple signals in these two states. Different combinations of signals lead to different outputs. Microchips can be easily damaged by high voltages. Due to this the voltages for the two logic states are standardized. Logic 1 is 5 V, while logic 0 is 0 V.

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