Bipolar Transistor, Thyristors, and Other Devices

• amplification - is the process of linearly increasing the amplitude of an electrical signal and is one of the major properties of a transistor.
• audio signal - is the electrical signal which is converted from human voice to an electrical signal.
• audio wave - is monitored in an electronics test instrument like oscilloscope.
• thyristors - refers to a class of solid state silicon switching devices made-up of four layer PNPN structure.
• breakdown voltage - is the voltage at which the blocking capability fails, and a massive amount of current rushes through.
• 100 - volts is the voltage that typical SCR can stand in either direction without breaking down.
• operating speed - SCR is specified in terms of "turn-on time" and "commutating turn-off time".
• 1-2 microseconds - typical switching speed of SCR.
• gate trigger current - specifies how much current is required to turn the device on.
• In our gate trigger current example, the specification says that no more than 100 microamps is required.
• gate trigger voltage - specifies the voltage required to trigger the device.
• in gate trigger voltage case, no more than 0.7 volts.
• triac - is a three terminal semiconductor for controlling current in either direction.
• diac - is a two terminal device that is used as a trigger device for either SCR or triac.
• quadrac - is basically a triac with a built-in trigger diac.
• silicon-controlled switch - is similar in construction to the SCR. However, it has two gate terminals, the cathode gate and the anode gate.
• SCR - is a uni-directional three terminal device used to control large current to a load.
• silicon unilateral switch - is another breakover device that conducts current in only one direction.
• silicon bilateral switch - this is another breakover device which is capable of triggering triacs. It has lower breakover voltage as compared to diacs.
• programmable unijuction transistor - is more similar to SCR except that its anode-to-gate voltage can be used to both turn on and turn off the device.
• shockley diode - this device acts as a switch and remains off until the forward voltage reaches a certain value; then it turns on and conducts.
• shockley diode - are also called four layer diode.
• Light-activated SCR - operates essentially as does the conventional SCR except it can also be triggered by light.
• phototransistor - is a light sensitive, collector-base pn junction.
• optical coupler - are designed to provide complete electrical isolation between an input circuit and an output circuit.