Summary
When a thyristor is in the forward-conducting state, all device junctions are forward biased and the device presents a minimum resistance to the forward current flow. At moderate and high injection levels, two of the three forward-biased junctions usually exhibit nearly equal but opposite potentials. Consequently, one junction contributes to the total device voltage drop. Since the junction voltage is a logarithmic function of the current, it varies only very slowly and its value is typically 0.8 to 1.0 V. for moderate or high current levels.
All regions of the device between the junctions, as well as metal contacts, contribute to the voltage drop across the device, but the most significant drop usually occurs in the long n base. This voltage drop is a sensitive function of the minority carrier lifetime in the n base, base width, and current density. At very high current densities the voltage drop consists basically of three components: the junction voltage drop, the n-base voltage drop, and the ohmic contact drop. At the extremely high currents, because of the injected carriers’ effect on mobility and lifetime, the voltage drop in the long base may also show an ohmic behavior.
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Blicher, A. (1976). Thyristor voltage drop in the on-state. In: Thyristor Physics. Applied Physics and Engineering, vol 12. Springer, New York, NY. https://doi.org/10.1007/978-1-4612-9877-9_7
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DOI: https://doi.org/10.1007/978-1-4612-9877-9_7
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