Transistor Types: BJT, JFET, and MOSFET

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MODULE I Transistor Types BJT JFET and MOSFETBipolar Junction Transistor BJT NPN and PNP Junction Field Effect Transistor JFET .
N channel and P channel Metal Oxide Semiconductor FET MOSFET Depletion type n and p channel andenhancement type n and p channel TYPE OF FET TRANSISTOR.
BJT Types NPN and PNP NPN a small input current and a positive voltage applied itsbase with VB VE allows a large current to flow from collector to emitter .
PNP a small output current and a negative voltage its base withVB VE allows a much larger current to flow from emitter to collector SYMBOLS FOR BJT NPN BJT How it works I.
When no voltage is applied attransistor s base electrons in theemitter are prevented from passingto the collector side because of thepn junction .
If a negative voltage is applied tothe base things get even worse asthe pn junction between the baseand emitter becomes reversebiasedresulting in the formation of.
a depletion region that preventscurrent flow NPN BJT How it works II If a positive voltage 0 6V isapplied to the base of an npntransistor the pn junction betweenthe base and emitter becomes.
forward biased During forwardbias escaping electrons are drawnto the positive base Some electrons exit through thebase but because the p type baseis so thin the onslaught ofelectrons that leave the emitter getclose enough to the collector sidethat they begin jumping into the.
collector Increasing the basevoltage increases the emitter tocollectorelectron flow Recall positive current flow is inthe direction opposite to theelectron flow current flows fromcollector to emitter .
BJT Water Analogy NPN Transistor in a Complete Circuit I Normally OFF No current passes from collector to emitter when base isnot activated .
NPN Transistor in a Complete Circuit II When VB VE we have an operating circuit Current passes from collector to emitter when base isactivated MODULE II JFET.
Junction field effect transistors like BJTs are three leadsemiconductor devices JFETs are used as electrically controlled switches current amplifiers and.
voltage controlled resistors Unlike BJTs JFETs do not require a bias current and are controlledby using only a voltage JFETs are normally on when VG VS 0 When VG VS 0 then JFETs become resistive to current flow.
through the drain source pair JFETs are depletion devices JFET Types Two types of JFETs n channel and p channel In n channel JFET a ve voltage applied its gate with VG VS reduces.
flow from drain to source It operates with VD VS In p channel JFET a ve voltage applied its gate with VG VS reducesflow from source to drain It operates with VS VD JFETs have very high input impedance and draw little or no input current if there is any circuit component connected to the gate of a JFET no current.
away from or sunk into this circuit JFET SYMBOLS Metal oxide semiconductor FET Similar to JFET A metal oxide insulator is placed the gate to obtain a high input.
impedance the gate input impedance approx 1014 Use of insulator as described above yields a low gate to channelcapacitance If too much static electricity builds up on the gate then the MOSFET.
may be damaged • Metal Oxide Semiconductor FET (MOSFET) – Depletion type (n- and p-channel) and enhancement type (n- and p-channel) TYPE OF FET TRANSISTOR. BJT Types • NPN and PNP. – NPN: a small input current and a positive voltage applied @ its base (with VB>VE)

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