The ratio of miss-to-hit is very important, having the special name BETA and is given ranges of values (often 50 to 300) on datasheets.īipolars have the very useful property of needing 0.058 volts more voltage across the base-emitter, for every 10:1 increase in current thru the transistor. Because the BASE region is very thin, most of the emitter-injected charges miss their targets and end up gathered up in the Collector region of that transistor. I won't go into any more details in this answer, there are plenty of resources into the behaviour of MOSFETs vs BJTs.īipolars operate by injecting small currents (electrons) into the base pin, and the emitter injects currents that attempt to cancel out the (opposite polarity) base currents. Both are transistors, but are used in different ways. In other words their behaviour is different. The voltage you apply across the gate controls how much current flows into the drain. That is to say the current flowing into the base of the transistor controls the current flowing into the collector.Ī MOSFET is a voltage controlled device. The reason for the difference in symbol and behaviour between a BJT and MOSFET is due to the way that the two types of transistor work differently, and exhibit different behaviour.Ī BJT transistor is a current controlled device. JFET (Junction FET), MESFET (Metal-Semiconductor FET). There are also more than two types - e.g. The top symbol, labelled "transistor" is the symbol for a BJT.In your picture, the symbols are misleadingly labelled. The picture shows two different packages, however this is no indication of type.Įqually the left one could be a MOSFET (e.g. : left one is "normal", and right is MOSFET : but there shapes is differentĪre they? Transistors come in packages of many shapes and sizes But lets assume for now you mean BJT when you say "normal". The question itself doesn't make much sense in that regard. : MOSFET transistor and normal transistorĪ MOSFET is a normal transistor - it's a Metal-Oxide-Semiconductor Field-Effect TransistorĪ BJT is another normal transistor - a Bipolar Junction Transistor
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