Solid state diode is composed of the anode and the cathode.
The anode of the solid state diode is composed of the positive carriers, while the cathode is composed of negative current carriers. In electronic technology, the positive current carriers are called holes, while the negative carriers are called electrons.
Between the anode and the cathode is the junction which has a repelling force. The junction separates the anode and the cathode. In other words, the work of the junction is to keep the opposite charge at the anode and the cathode be separated, and prevent them from combining. the force of the junction used to separate the opposing charges is called junction voltage, or barrier voltage.
In germanium solid state diode, the junction voltage is approximately 0.3 volts while in silicon state diode, the junction is approximately 0.7 volts.
If we apply voltage to the diode to force the opposing charges at the cathode and anode to combine, recombination of these charges will take place and current will flow in the diode, this is called the forward bias.
Now,if we apply reverse or invert the connection of the applied voltage, No current flows in the diode, this is called the reverse bias.
When we test the solid state diode with a multitester, what we are doing is applying a bias voltage to the diode, by using battery inside the said multitester.
Always remember that when we adjust the multitester to test the solid state diode what we are actually doing is connecting it to its internal battery. and we can do this by adjusting its range switch to ohms or ohmmeter range.
We must not forget the following:
When using the multitester to test the solid state diode (or any state solid state devise), it must be adjusted at Rx10 or lower. Our reasons for doing this is to avoid damage to the junction of the diode and to obtain accurate test results.
When the pointer of the multitester deflects or moves forwards the right side, it means that current flows through the solid state diode and the said diode is forward biased by internal battery of the multitester.
When the pointer of the multitester does not deflect or does not move to the right, it means that there is no current flowing in the solid state diode. and that said diode is revered biased.
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