Transistor as a Switch

Transistor as a switch is the simplest application of the devices. A transistor can be used for switching operations or opening or closing of the circuit. The main or basic concept of this operation relies on it’s operation generally low voltage DC is on or off by the transistor in this mode. The both type of the PNP and NPM transistor are used as switches. The terminal transistor can be handled different from a single amplifier by biasing both the NPM and PNP bipolar transistor with “ON/OF” static switch. One of the basic and main use of the transistor is to transform a DC signal “ON” or “OFF” is solid state switch. Many devices such as LED’s, lights requires very small milliamps logic level DC voltage and can directly driven by the output of a logic. If any circuit requires Bipolar Transistor Switch then the biasing of the transistor is either PNP or NPM which are arranged for operating the transistor for both sides of the “I-V” characteristics curves.

The operating area of the transistor switch called saturation region and the cut-off Region.

Transistor as a Switch

A transistor is a three-terminal semiconductor that regulates the current or voltage flow and acts or operates as a switch or gate for signals. The devices in the electronics and electricals are the regulated values which allows the weak signal to regulate the large amount of flow to the nozzle that regulates the flow of current. The transistors quantifies thousands and millions of transistors which are interconnected and embedded into small integrated chip or circuit boards. A transistor switch is used for opening or closing the circuit, which means we use a transistor is used as a switch in electrical devices only for low-voltage application devices due to their low power consumption. The transistors work as same as the switch when is it in cutoff and saturation regions.

Table of Content

  • Transistors as a Switch
  • Construction
  • Operating Region
  • PNP as a Transistor
  • Darlington Transistor Switch
  • Applications

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What are Transistors as a Switch?

A simple transistor is a three-terminal semiconductor which is used as an amplifier. The transistor as a switch is used for turning ON or OFF a circuit and the transistor is used as an amplifier for amplifying the current. In digital circuits, the ones and zeros are stored in the form of bits(0 or 1 ). The advantage of using the transistor as the switch is that it can control a large amount of current with a small amount of current called gain....

Construction of Transistor

The transistor is a three terminal solid state device which have two diodes in continuation. It has two PN junctions. The transistor have three terminals that are drawn out of three semiconductors materials present in it. This structure form two types of transistors PNP and NPN which means N-type material between the two P type and the other is P type between two N types....

Transistor as a Switch

Transistor as a switch is the simplest application of the devices. A transistor can be used for switching operations or opening or closing of the circuit. The main or basic concept of this operation relies on it’s operation generally low voltage DC is on or off by the transistor in this mode. The both type of the PNP and NPM transistor are used as switches. The terminal transistor can be handled different from a single amplifier by biasing both the NPM and PNP bipolar transistor with “ON/OF” static switch. One of the basic and main use of the transistor is to transform a DC signal “ON” or “OFF” is solid state switch. Many devices such as LED’s, lights requires very small milliamps logic level DC voltage and can directly driven by the output of a logic. If any circuit requires Bipolar Transistor Switch then the biasing of the transistor is either PNP or NPM which are arranged for operating the transistor for both sides of the “I-V” characteristics curves....

Operating Region

Operating Region...

PNP as a Transistor

In general the logic and microcontroller are able to drive only the small loads by them but sometimes the load need to switched the requires more current then the required current controlling component which is supplied. In general case the transistors are used switch to reach the required current and voltage for amplification is achieved. When the PNP is used the microcontroller have only sink the base current. The emitter and collector path of the PNP transistor becomes high impedance or conductive....

Darlington Transistor Switch

Darlington transistor consists of two bipolar transistors is connected in such a way that the current amplified by the first transistor is amplified further by the second one. This type of transistor which use multiple switching transistor because when the DC gain of the one bi-polar transistor is very low for switching the load voltage or current. In construction or configuration a small input BJT(Bipolar Junction Transistor) is involved in switching on and off a bigger current holding output BJT transistor....

Configuration Darlington Transistor Switch

In Darlington Transistor Switch two NPN or PNP are connected together in a wat that the emitter current of the first transistor T1 becomes the base of the second transistor T2. So the T1 is connected as an emitter and the T2 is common emitter amplifier....

Applications of Transistor as a Switch

The transistor as a switch is the main application in the LED’s. The operation on relay are managed by creating the necessary circuit changes in order to connect and control the external devices. The DC motors can also be controlled and monitored. It is used for starting the engine on or off. The speed of the motors are modified by changing the transistor frequency values. The light bulb is the simple example of this switches. It can the turn on if the setting is bright and turn off depending on the dark surrounding for which we use LDR. The thermistors are controlled using the switches which detects the ambient temperature sensed low and the resistance decreased when the temperature is high....

Conclusion

In this Article, we have gone through basics of the Transistor, we have also looked at the Construction of the Transistor, then we have gone Through the Topic Transistor as a Switch, In this we have seen the operation Region(Cut-off and Saturation Region),then we have seen PNP Transistor, Darlington Switch with its Configuration, In Configuration of Darlington Switch we have gone through Digital Logic Transistor Switch and Darlington Transistor Switch, at last we have seen some Applications of Transistor as a Switch....

FAQs on Transistor as a Switch

1. Which region of the transistor is very highly doped?...