Electronics lec 12
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This document provides an introduction to various types of electronics components including junction field effect transistors, MOSFETs, TRIACs, and insulated gate bipolar transistors. It describes junction FETs as voltage controlled three terminal unipolar semiconductor devices and discusses N-channel and P-channel types. MOSFETs are described as operating similarly to JFETs but having an electrically isolated gate. TRIACs are bidirectional thyristor devices that can switch AC power in both directions. Insulated gate bipolar transistors combine advantages of MOSFETs and bipolar junction transistors for use in power electronics.
Electronics lec 12
- 1. Electronics an Introduction Eng. : Mohamed ElKenany
- 2. Contoso S u i t e s 2 Electronics :-
- 3. Contoso S u i t e s 3 Electronics :- ▪ Junction Field Effect Transistor ▪ voltage controlled three terminal unipolar semiconductor ▪ Field Effect Transistor is a three terminal unipolar semiconductor device that has very similar characteristics to those of their Bipolar Transistor ▪ low power consumption ▪ N-channel FET and the P-channel FET ▪ The control of current flowing in this channel is achieved by varying the voltage applied to the Gate ▪ “Unipolar” device that depends only on the conduction of electrons (N-channel) or holes (P-channel). ▪ There are two main types JFET , IGFET which is more commonly known as MOSFET ▪ In this pinch-off region the Gate voltage, VGS controls the channel current and VDS has little or no effect. ▪ It is essential that the Gate voltage is never positive since if it is all the channel current will flow to the Gate and not to the Source, the result is damage to the JFET
- 4. Contoso S u i t e s 4 Electronics :- ▪ Junction Field Effect Transistor ▪ FET acts more like a voltage controlled resistor which has zero resistance when VGS = 0 and maximum “ON” resistance ( RDS ) when the Gate voltage is very negative. Under normal operating conditions ❑Ohmic Region – When VGS = 0 the depletion layer of the channel is very small and the JFET acts like a voltage controlled resistor. ❑Cut-off Region – This is also known as the pinch-off region were the Gate voltage, VGS is sufficient to cause the JFET to act as an open circuit as the channel resistance is at maximum. ❑Saturation or Active Region – The JFET becomes a good conductor and is controlled by the Gate-Source voltage, ( VGS ) while the Drain-Source voltage, ( VDS ) has little or no effect. ❑Breakdown Region – The voltage between the Drain and the Source, ( VDS ) is high enough to causes the JFET’s resistive channel to break down and pass uncontrolled maximum current.
- 5. Contoso S u i t e s 5 Electronics :- ▪ MOSFET ▪ MOSFET’s operate the same as JFET’s but have a gate terminal that is electrically isolated from the conductive channel ▪ Insulated Gate Field Effect Transistor , Metal Oxide Semiconductor Field Effect Transistor or IGFET or MOSFET ▪ Gate electrode which is electrically insulated usually silicon dioxide, commonly known as glass ▪ “NO current flows into the gate” ▪ MOSFETs very high input resistance can easily accumulate large amounts of static charge resulting in the MOSFET becoming easily damaged ▪ it is possible to bias the gate of a MOSFET in either polarity, positive (+ve) or negative (-ve). Enhancement type vs Depletion type
- 6. Contoso S u i t e s 6 Electronics :- ▪ MOSFET
- 7. Contoso S u i t e s 7 Electronics :- ▪ TRIAC ▪ A Triac is a high-speed solid-state device that can switch and control AC power in both directions of a sinusoidal waveform ▪ Member of the thyristor family ▪ “Bidirectional” device ▪ The Triac can be triggered into conduction in either direction. ❑ Ι + Mode = MT2 current positive (+ve), Gate current positive (+ve) ❑ Ι – Mode = MT2 current positive (+ve), Gate current negative (-ve) ❑ ΙΙΙ + Mode = MT2 current negative (-ve), Gate current positive (+ve) ❑ ΙΙΙ – Mode = MT2 current negative (-ve), Gate current negative (-ve)
- 8. Contoso S u i t e s 8 Electronics :- ▪ TRIAC
- 9. Contoso S u i t e s 9 Electronics :- ▪ Insulated Gate Bipolar Transistor ▪ The IGBT is a power switching transistor which combines the advantages of MOSFETs and BJTs ▪ Takes the best parts of these two types of common transistors the high input impedance and high switching speeds of a MOSFET with the low saturation voltage of a bipolar transistor ▪ mainly used in power electronics applications such as inverters, converters and power supplies, were the demands of the solid state switching device