The transistors BJT and MOSFET square measure each helpful for amplification and shift applications. Yet, they need considerably completely different characteristics.

BJT, as in Bipolar semiconductor unit, could be a semiconductor unit that replaced the vacuum tubes of the previous days. The device could be a current-controlled device wherever the collector or electrode output could be a operate of this within the base. Basically, the mode of operation of a BJT semiconductor is driven by this at the bottom. The 3 terminals of a BJT semiconductor square measure referred to as the electrode, Collector, and Base.

A BJT is really a chunk of the element with 3 regions. There square measure 2 junctions in them wherever every region is called otherwise ‘“ the P and N. There 2 form of BJTs, the NPN semiconductor, and also the PNP semiconductor. the kinds disagree in their charge carriers, wherein, NPN has holes as its primary carrier, whereas PNP has electrons.

The operation principles of the 2 BJT transistors, PNP and NPN, square measure much identical; the sole distinction is in biasing, and also the polarity of the ability offer for every sort. several like BJTs for low current applications, like for shift functions for example, just because they’re cheaper.

Metal chemical compound Semiconductor junction transistor, or just MOSFET, and generally MOS semiconductor, could be a voltage-controlled device. in contrast to the BJT, there’s no base current gift. However, there’s a field created by a voltage on the gate. this permits a flow of current between the supply and also the drain. This current flow could also be pinched-off or opened, by the voltage on the gate.

In this semiconductor, a voltage on associate oxide-insulated gate conductor will generate a channel for physical phenomenon between the opposite contacts ‘“ the supply and drain. What’s nice regarding MOSFETs is that they handle power a lot of with efficiency. MOSFETs, nowadays, square measure the foremost common semiconductor utilized in digital and analog circuits, substitution the then very hip BJTs.

As explained in my previous articles, BJT is a current-controlled device wherever MOSFET is voltage-controlled, each with distinctive characteristics and their professionals and cons. There isn’t a straight-forward and definite answer to the question that one is best.

When selecting that one to use in your application, one must think about several factors as well as power level, drive voltage, load voltage, switching speed, efficiency, cost, etc.

I will chiefly specialize in low power consumption applications e.g. driving some LEDs or 5V DC motor etc, since most of the readers on this diary square measure of Arduino and Raspberry Pi hobbyists.


01. BJT Transistor : [ See Buy Click Banggood | Amazon ]

02. MOSFET : [ See Buy Click Banggood | Amazon ]

Load Driving

When used with Arduino which may solely turn out associate DC output voltage of 5V, we tend to area unit restricted to exploitation logic level MOSFET. they’re not as common as normal MOSFET that needs a minimum of 10V or a lot of Vgs (gate-source voltage) to totally activate.

On the opposite hand, BJTs that may be driven by Arduino (~5V DC) area unit easier to seek out, and customarily cheaper.

Therefore BJTs area unit a lot of appropriate than MOSFETs for driving low-power LEDs and similar devices from small Controllers Unit (e.g. Arduino).

BJT will switch quicker than MOSFET thanks to the less capacitance at the management pin. but MOSFET is a lot of tolerant to heat (stable to thermal changes) and may simulate a decent resistance.

At low power and voltages application – e.g. but 10V and around 1A, tiny BJT may be a decent selection. Bipolar wear state voltage drops (Vsat) dependent on load current, drive current & specific device kind. A MOSFET has an associate on resistance Rdson instead of Vsat. Rdson is dependent on drive voltage, load current. Rdson will increase with temperature and will double close temperature values.

Fig: BJT


Power Consumption Efficiency

MOSFET is sometimes a lot of economical switches for power provides. BJT can consume a lot of power as a result of it’s wasting current once it’s switched on. Also, the BJT usually incorporates a zero.3v free fall within the input pin, and it takes heaps of base current to try to that.

Transistors are usually connected along to create helpful circuits. as an example, the MOSFETs is simply placed in parallel, however, the BJT cannot unless external electrode resistors are supplementary. The external resistance generates extra potency losses.

In a powered device wherever you’ve got restricted power and therefore the load is variable and sometimes low, victimization BJT could be a dangerous plan. If a BJT is employed to power one thing with a sure current draw like LEDs, victimization BJT isn’t as dangerous. as a result of you’ll be able to merely set the base-emitter current to be a tiny low fraction of the light-emitting diode current to attain higher potency.

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