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Why majority carrier devices have higher ON state resistance compared to the ON state resistances of minority carrier devices?

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    \$\begingroup\$ What types of devices are you calling "majority carrier devices" and "minority carrier devices"? \$\endgroup\$
    – The Photon
    Dec 18, 2018 at 18:09
  • \$\begingroup\$ Majority carrier devices are those which have either positive or negative conducting charge carriers but not both. eg MOSFET while minority carrier have both types. eg SCR, BJT. \$\endgroup\$
    – Jibe
    Dec 18, 2018 at 20:21

1 Answer 1

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I would not say that majority carrier devices have higher "ON state resistance" than minority carriers.

Comparing the two most common types, FETs and BJTs, FETs have actually lower large signal resistance even though this is a majority carrier device. The reason for this is because a highly inverted channel in the FET and therefore a good conductive channel is not influenced by the drain-source voltage but by the gate overdrive. A large overdrive will flood the channel with majority carriers and allow for super high conductance.

For a BJT, however, if you want to keep the device out of saturation and in forward active region, you need to make sure that the base-emitter junction is forward biased in addition to keeping the base-collector junction forward biased. This inherently constrains the collector emitter voltage to a value higher than the saturation voltage, which limits your on-state resistance. Another way to see this is to consider that with a minority carrier device, the act of conduction is done through diffusion, which couples your collector emitter voltage to the amount of charge flowing through the base. This will increase the on-state resistance.

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