Mai yana NPN Transistor?

Zanen da NPN Transistor?

NPN Transistor Tushen

NPN transistor yana da tushen mai sauƙi a amfani da shi a cikin masu kisan junction bipolar, inda lura mai P-type ta kasance a kan biyu na N-type.

Takarda NPN Transistor

Kamar yadda aka bayar a ƙarshe, NPN transistor yana da biyu na junctions da uku na terminals. Takarda NPN transistor yana ɗauke a cikin hanyar zuwa na ɗaya.

Luran da kuma collector suna da tsari mafi yawa daga base. Emitter yana da zama mai yawa. Saboda haka, zan iya ci gaba da adadin charge carriers mafi yawa zuwa base.Base yana da zama mai kadan da kuma yana ɗaya ɗaya daga abubuwan da suka fi. Yana tara mafi yawan charge carriers zuwa collector wanda an tsafta shi daga emitter.Collector yana da zama mai yawa da kuma yana ƙoƙarin charge carriers daga lura.

Alamun NPN Transistor

Alamu na NPN transistor yana ɗauke a cikin hanyar zuwa na ɗaya. Alama ta ɗaukan ya nuna yadda Collector current (IC), Base current (IB) da Emitter current (IE) ke ɗauke.

Siffar Farko

Junction da ke bayar da VEE, baki daya da ke bayar da VCC.

A nan, terminali mai kadan na supply source (VEE) ana ce a N-type semiconductor (Emitter). Duk da haka, a nan, terminali mai yawa na supply source (VCC) ana ce a N-type semiconductor (Collector).

Depletion region na emitter-base yana da tsari mafi yawa daga depletion region na collector-base (Note that the depletion region is a region where no mobile charge carriers are present and it behaves like a barrier that opposes the flow of the current).

A N-type emitter, majority charge carrier yana da electrons. Saboda haka, electrons suna ɗauke daga N-type emitter zuwa P-type base. Kuma saboda electrons, current zai ɗauke a junction na emitter-base. Wannan current yana nufin Emitter current IE.

Electrons suna ɗauke a base, wanda yake da tsari mafi yawa da kuma yana da kadan da kadan holes don recombination. Saboda haka, mafi yawa electrons suna ɗauke a base, kuma mafi yawan electrons suna recombine.

Saboda recombination, current zai ɗauke a circuit, kuma wannan current yana nufin Base current IB. Base current yana da tsari mafi yawa daga Emitter current. Typically, it is 2-5% of the total Emitter current.

Mafi yawa electrons suna ɗauke a depletion region na collector-base junction da kuma suna ɗauke a collector region. Current na remaining electrons yana nufin Collector current IC. Collector current yana da tsari mafi yawa daga Base current.

NPN Transistor Circuit

Circuit na NPN transistor yana ɗauke a cikin hanyar zuwa na ɗaya.

Diagramma yana nuna yadda voltage sources ke ce: collector ana ce a terminali mai yawa na VCC through a load resistance RL, which limits the maximum current flow.

Terminali na base ana ce a terminali mai yawa na base supply voltage VB with base resistance RB. Base resistance yana amfani don limit the maximum base current.

Idan transistor yana ɗauke, yana ɗauke a large collector current to flow, driven by a smaller base current entering the base terminal.

By KCL, Emitter current yana nuna addition of Base current and Collector current.

Mode na Operation na Transistor

Transistor yana ɗauke a different modes or regions depends on the biasing of junctions. It has three modes of operation.

• Cut-off mode

• Saturation mode

• Active mode

• Cut-off Mode

A cut-off mode, both junctions are in reverse bias. In this mode, the transistor behaves as an open circuit. And it will not allow the current to flow through the device.

Saturation Mode

In the saturation mode of a transistor, both junctions are connected in forward bias. The transistor behaves as a close circuit and current flow from collector to emitter when the base-emitter voltage is high.

Active Mode

In this mode of a transistor, the base-emitter junction is forward bias and collector-base junction is reverse biased. In this mode, the transistor operates as a current amplifier.

The current flows between emitter and collector and the amount of current are proportional to the base current.

NPN Transistor Switch

The transistor operates as switched ON in saturation mode and switched OFF in cut-off mode.

When both junctions are connected in the forward bias condition and sufficient voltage is given to input voltage. In this condition, collector-emitter voltage is near to zero and the transistor operates as a short circuit.

In this condition, the current will start flowing between collector and emitter. The value of the current flowing in this circuit is,

When both junctions are connected in reverse bias, the transistor behaves as an open circuit or OFF switch. In this condition, the input voltage or the base voltage is zero.

Therefore, the entire Vcc voltage appears across the collector. But, because of the reverse bias of the collector-emitter region, the current cannot flow through the device. Hence, it behaves as an OFF switch.

The circuit diagram of a transistor in the cut-off region is as shown in the below figure.

NPN Transistor Pinout

The transistor has three leads; collector (C), Emitter (E), and Base (B). In most of the configurations, middle lead is for Base.

To identify the emitter and collector pin, there is a dot on the surface of the SMD transistor. The pin which is exactly below this dot is a collector and the remaining pin is the emitter pin.

If the dot is not present, all pins will be placed with uneven space. Here middle pin is base. The closest pin of a middle pin is emitter and the remaining pin is a collector pin.