Power MOSFETs, just like their integrated circuit counterpart, can be of two types (i) depletion type and (ii) enhancement type. Both of these can be either n- channel type or p-channel type depending on the nature of the bulk semiconductor. Fig 6.1 (a) shows the circuit symbol of these four types of MOSFETs. Buy 2N7335 JANTXV, Learn more about 2N7335 4 P-channel Power MOSFET (four P-channel power MOS FET), View the manufacturer, and stock, and datasheet pdf for the 2N7335 at Jotrin Electronics. In this article, we will learn the Basics of MOSFET, its internal construction, how it works, and how to use them in your circuit designs.
ADMIN·Published · UpdatedIt is interesting to know why Now a days Power Electronics Design Engineers prefer-MOSFET over BJT in their applications.
Power-MOSFET has several features different from that of Power BJT. Those are discussed in this post. Before proceeding further, it is good to know about the Power Mosfet and Power BJT. Our earlier posts explains about these topics.
Click here to know about the basics of Power BJT
Click here to know about Power MOSFET.(i) Power-MOSFET(Metal Oxide Semiconductor Field Effect Transistor) has lower switching losses but its on-resistance and conduction losses are more. In contrast to this, BJT(Bidirectional Junction Transistor) has higher switching losses but lower conduction losses.
MOSFETs are majority carrier device, means flow of current inside the device is carried out either flow of electrons(N-Channel MOSFET) or flow of holes(P-Channel MOSFET). So when the device turns off, reverse recombination process won’t happen. It leads to short turn ON/OFF times. As switching time is less, loss associated with it less.
So for high frequency applications, where the switching loss is major impact in total power loss of the circuit, this device is the right choice.
On the other hand, for applications having lower operating frequencies BJT is superior.
(ii) MOSFET is voltage controlled device whereas BJT is current controlled device.
Mosfet operation is controlled by gate-source voltage(V
GS). In BJT, the operation is controlled by base current. As we know that providing constant voltage is easier than providing constant current in electrical circuits. So Mosfet’s gate drive circuit is less complex than BJT’s base drive circuit.High Power Mosfets
(iii) MOSFET has positive temperature coefficient for resistance. So parallel operation is easy. BJT has negative temperature coefficient, so current-sharing resistors are mandatory during parallel operation of BJTs.(iv) The major difference between Power-MOSFET and Power-BJT is, that the Power-MOSFET do not have the secondary breakdown problem whereas Power-BJT suffers from secondary breakdown issue.
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