![]() This forward current flow through the diode is depends on the voltage applied and the external load resistance. Therefore, it acts like a short circuit and allows the current to flow until the current reaches to the holding current level of the diode. ![]() Once the break over voltage is reached (as the forward voltage is increased), it exhibits a very low resistance due to the breakdown of junction J2. Until the voltage across the diode is less than the break over voltage, as an open switch this diode exhibits a very high resistance and allows no current to flow through it. When the voltage is applied to the this diode in such a way that anode is made positive with respect to cathode, junctions J1 and J3 are forward biased and J2 is reverse biased. Therefore, as the base emitter junctions, J1 and J3 must be forward biased and as a collector base junction, J2 must be reverse biased for linear operation.Īs discussed above, the these diodes consists of three junctions J1, J2 and J3. The junction J1 is formed at the emitter base junction of T1, J2 is at common connected base collector junction between T1 and T2, and the J3 is at base emitter junction of T2. The equivalent circuit of this diode using two transistors is shown in above figure where in the collector of a transistor T1 is connected to the base of T2. The construction of this diode is simple: it is constructed by joining the four layers to form PNPN junction. The basic construction, two transistor analogy and symbol of the shockley diode are shown in below figure. ![]() These diodes have only two states, either ON or OFF that’s why these are classified as a thyristors. It functions like a normal diode without any trigger inputs, in reverse biased condition, no current flows through it and in forward biased condition current flows through it when the voltage across it is more than the break over voltage of it. The Shockley diode or PNPN diode is a four layer (P-N-P-N), two terminals (namely anode and cathode) semiconductor switching device. ![]()
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