Solid-state semiconductor circuit elements {transistor, electronic}| amplify current.
types
N-type semiconductor, P-type semiconductor, and N-type semiconductor can join in sandwich {NPN transistor}. P-type semiconductor, N-type semiconductor, and P-type semiconductor can join in sandwich {PNP transistor}. NPN or PNP transistors are bipolar transistors {junction transistor}, with two junctions. Weak signals control current flow. Junction transistors are current operated.
parts
Transistors have cathode emitter, anode collector, and base controller. Collector is between emitter and base. In PNP transistors, electrons flow from emitter to middle collector and from base to middle. In NPN transistors, electrons flow from middle collector to emitter and from middle to base.
process
Holes and electron diffusion across semiconductor np junction continues until electric force equilibrium, preventing further diffusing. Voltage is across emitter and base and across collector and emitter. Applying small positive charge to base attracts electrons and amplifies current 10^5 times. Electron flow from emitter to collector multiplies directly with voltage from base to emitter.
surface barrier
A depletion layer {space charge, transistor} between metal and semiconductor can control conductivity {point contact semiconductor} {surface barrier transistor}.
field effect
Electric field at right angles to silicon surface causes lateral conductance {field-effect transistor}. Insulated field plate can have field that induces conducting surface channel between two surface pn junctions {gate}, as in field-effect transistors, such as metal oxide semiconductors. Field-effect transistors have slow response and high impedance. They are voltage operated, rather than current operated.
electron tubes
Transistors can replace all electron tube types.
In PNP transistors, electrons flow from emitter to collector, and from other sandwich side {base, transistor} to middle.
In PNP transistors, electrons flow from emitter to middle {collector, transistor}, and from base to middle.
In PNP transistors, electrons flow from one sandwich side {emitter, transistor} to collector, and from base to middle.
5-Physics-Electromagnetism-Conductivity-Semiconductor
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Date Modified: 2022.0225