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Recognition and Measurement of Electronic Components
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This video mainly explains the characteristics and working conditions of diodes
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Diode characteristics
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The diode has the characteristics of unidirectional conduction and reverse cut-off
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In layman's terms, the power supply of a diode can only flow from the positive pole to the negative pole,
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not from the negative pole to the positive pole
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For a diode to conduct, it needs an operating condition
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Diodes made of different materials have different conduction and working conditions
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For example, the conduction condition of the silicon diode is that
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the voltage of the positive pole must be greater than the voltage of the negative pole by 0.7V or more
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When the conditions are met,
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the voltage of the positive pole can flow to the negative pole
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If this condition is not met, the diode is in the cut-off state
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The working condition of the germanium diode is that
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the positive voltage is 0.3V or more higher than the negative voltage
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When the conditions are met,
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the voltage of the positive pole can flow to the negative pole
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If this condition is not met, the diode is also off
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Below is a small animation to understand the diode conduction working conditions
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The wide end of the diode represents the positive pole,
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and the pointed end represents the negative pole.
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The conduction condition of the silicon tube is that
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the positive pole is greater than the negative pole by 0.7V
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Now the negative pole has a 3V power supply,
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how high the voltage needs to be added to the positive pole,
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can the positive pole power supply flow to the negative pole?
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3 plus 0.7 is 3.7V
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Therefore, when the positive voltage is at least 3.7V,
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the positive voltage can flow to the negative
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If the positive voltage is lower than 3.7V, the diode is in the cut-off state,
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the positive voltage cannot pass, and the negative voltage cannot pass
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If an 8V power supply is applied to the positive pole of the diode,
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what is the voltage at the negative pole of the diode?
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The voltage drop of the silicon tube is 0.7V,
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8 minus 0.7 is 7.3
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The voltage of the negative pole is about 7.3V at this time
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The conduction condition of the germanium tube is that
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the positive voltage is greater than the negative voltage by 0.3V or more,
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and the voltage drop is 0.3V
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If it is a germanium tube, apply 8V power supply to the positive electrode,
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and it will be about 7.7V after it is turned on
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In mobile phones, most of the germanium tubes are used
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The advantage of the germanium tube is that the voltage drop is relatively low,
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and the power loss will be relatively small
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Ok, that's it for this lesson
