![]() ![]() Schematic Symbols for Common Electrical Components.They are used in opto-couplet or opto-isolator to electrically isolate two circuits by using an LED between them. Photo FET Transistor is a light dependent FET that switches when the light intensity upon its junction changes. positive logic voltage usually of 5v at gate-source starts conduction of maximum current. They are used for switching heavy loads when applied with digital logic i.e. Logic level FET transistors are designed to be used with digital logic systems. They operate the same as depletion type MOSFET but the only difference is that depletion type normally conducts while enhancement type normally don’t conduct when there is zero gate-source voltage. This is an enhancement type dual gate MOSFET. For example, the amplification factor of signal at gate 1 can be controlled by varying the signal at gate 2 thus providing automatic control for signal of various magnitude. The gates control the amplification factors more precisely. It grounds the substate.ĭual gate MOSFET is a special type of MOSFET that incorporate two individual gates in series. It is shorted with the source terminal of MOSFET for operation. This depletion type MOSFET has an extra separate terminal for the bulk or body. It is usually internally connected with the source terminal which is why they are omitted from their symbol to show a clear schematic with less clunky wiring. It is neither an input nor an output terminal but it is used for grounding the substrate. The extra terminal is known as Bulk or body terminal. Such type of enhancement MOSFET has four terminals. Enhancement type resembles a normally open switch while Depletion type resembles normally closed type switches. They turn ON by applying positive gate-source voltage for N channel & by negative gate-source voltage for P channel Enhancement MOSFET. The Enhancement type MOSFET do not normally conduct when gate-source voltage is at zero. They switch OFF by applying positive or negative gate-source voltage for P channel or N channel MOSFET respectively. ![]() The Depletion type MOSFET is normally ON at zero gate-source voltage. It is a voltage controlled current device. MOSFET or Metal-oxide Semiconductor FET is another field effect transistor whose gate is completely isolated from the current carrying channel that is why it is also known as IGFET (insulated Gate FET). The main advantage of this Sziklai pair is that it switch on with 0.7v while the total gain remains the same as in Darlington pair. The Sziklai transistor is made from combining two NPN & PNP transistors in Darlington pair formation. the total gain of Darlington transistor is the product of gains of individual BJT & the voltage drop is twice at base-emitter. It can be made from NPN or PNP transistors by connecting it in this configuration. It is a special type of transistor made by connecting the emitter of one BJT with the base of another BJT to increase the current gain & sensitivity. The voltage at the gate terminal switches the PUT on & off when it crosses its cutoff level. PUT or programmable UJT is a four PN layer device just like the thyristors but it operate like UJT if programmed with two external resistors.
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