Why do we use PNP transistor?

Why do we use PNP transistor?

PNP transistors are used to source current, i.e. current flows out of the collector. PNP transistors are used as switches. These are used in the amplifying circuits. PNP transistors are used when we need to turnoff something by push a button.

Why transistor is used in fire alarm system?

A BC547 NPN transistor drives a buzzer or an Led at the output as it detects a fire. The working of a fire sensor is quite easy and simple. The transistor turns on whenever it gets the base voltage of 0.7V through the resistor. As the circuit senses the fire it decreases the resistance at the base.

What is a PNP transistor and how does it work and what is it used for?

The PNP transistor is a type of transistor in which one n-type material is doped with two p-type materials. It is a device that is controlled by the current. Both the emitter and collector currents were controlled by the small amount of base current. Two crystal diodes are connected back-to-back in the PNP transistor.

Why we use NPN not PNP?

As the electrons have higher or faster mobility than holes, the conductivity also more. For this reason, NPN transistors are more preferable than PNP transistors because the NPN transistor provides more conductivity. We know that in electronic circuits all the negative(-ve) or common terminals are grounded.

What is the work of PNP transistor?

The PNP transistor turns on when a small current flows through the base. The direction of current in PNP transistor is from the emitter to collector. The letter of the PNP transistor indicates the voltage requires by the emitter, collector and the base of the transistor.

Are PNP transistors used?

PNP transistors are used in amplification circuits. PNP transistors are used in Darlington pair circuits. PNP transistors are used in robotic applications. PNP transistors to control current flow in heavy applications.

Which of the following is used in fire alarm?

Carbon monoxide detectors are known also as CO fire detectors are electronic detectors used to indicate the outbreak of fire by sensing the level of carbon monoxide in the air. Carbon monoxide is a poisonous gas produced by combustion.

How can a PNP transistor be used in a circuit?

Example: PNP Transistor Circuit

1. Step 1: The Emitter. First of all, to turn on the PNP transistor, you need the voltage on the base to be lower than the emitter.
2. Step 2: What You Want To Control. When the transistor turns on, the current can flow from the emitter to the collector.
3. Step 3: The Transistor Input.

Why we dont use PNP transistor?

There are two basic reasons for the preference for NPN BJTs over PNP devices: The mobility of N type charge current carriers (negative electrons) in silicon (Si) is more than two times greater than the mobility of P type charge carriers (positive holes) in Si. Resulting in faster transistor operating speed.

Why NPN transistor is more preferred over PNP?

The majority charge carriers in an NPN transistor are electrons and the majority carriers in a PNP transistor are holes. The electrons have better mobility than holes. Therefore, NPN transistors are preferred over PNP transistors.

How does transistor work in a circuit?

A transistor works when the electrons and the holes start moving across the two junctions between the n-type and p-type silicon. The small current that we turn on at the base makes a big current flow between the emitter and the collector. So the base current switches the whole transistor on and off.

What kind of transistors are used in fire alarm circuit?

This fire-alarm circuit is designed in such a way that when the system receives temperature that exceeds to the permeable limit, this tool will automatically generate alarm. To define a proper tool, the proposed system will use the combination of silicon NPN transistor Q1 [BC109] and PNP Germanium Transistor Q2 [AC188].

Which is an example of a PNP transistor?

PNP Transistor Example. Consider a PNP transistor, which is connected in the circuit with the supply voltages VB = 1.5V, VE = 2V, +VCC = 10V and –VCC = -10V. And also this circuit connected with the resistors of RB = 200kΩ and RE = RC (or RL) = 5kΩ. Now calculate the current gain values (α, β) of the PNP transistor.

When does a transistor turn on a fire sensor?

The transistor turns on whenever it gets the base voltage of 0.7V through the resistor. As the circuit senses the fire it decreases the resistance at the base. Due to which the voltage across the base terminal increases or becomes equal to 0.7V which turns the transistor ON. The Led starts glowing to indicate the fire.

How does a BC547 NPN work on a fire sensor?

A BC547 NPN transistor drives a buzzer or an Led at the output as it detects a fire. The working of a fire sensor is quite easy and simple. The transistor turns on whenever it gets the base voltage of 0.7V through the resistor.