Why we are using PNP as current source?

Why we are using PNP as current source?

Here the amplifying transistor is connected to ground; so, the active load should be a source whose output “pushes” a current into the collector/drain. Its output is the collector/drain; so its emitter has to be connected to +V. That is why this arrangement (kind of connection) requires a p-n-p (PMOS) transistor.

What is the function of a 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.

How does a PNP transistor work as a switch?

For a PNP transistor, the Emitter potential must be positive with respect to the Base. Then the transistor operates as a “single-pole single-throw” (SPST) solid state switch. With a zero signal applied to the Base of the transistor it turns “OFF” acting like an open switch and zero collector current flows.

How does a PNP junction work?

A PNP transistor is a bipolar junction transistor constructed by sandwiching an N-type semiconductor between two P-type semiconductors. A PNP transistor has three terminals – a Collector (C), Emitter (E) and Base (B). The PNP transistor behaves like two PN junctions diodes connected back to back.

Can I use PNP instead of NPN?

Generally, the PNP transistor can replace NPN transistors in most electronic circuits, the only difference is the polarities of the voltages, and the directions of the current flow. PNP transistors can also be used as switching devices and an example of a PNP transistor switch is shown below.

What is difference between PNP and NPN transistor?

In a PNP transistor, the majority charge carriers are holes while in NPN the majority charge carriers are electrons….

Difference Between NPN and PNP Transistor
One P-type semiconductor is sandwiched between the two N-type semiconductors.	It is made of up two P-type material layers with N-type sandwiched between them.

Where 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.

What is the function of PNP and NPN transistor?

NPN transistors are used as a sink to the current i.e., current flows to the Collector. It means the current points inwards. PNP transistors are used as a source to the current i.e., current flows out of the Collector. In the NPN transistor, electrons are important current carriers.

How does current flow through a transistor?

We know that in transistors and diodes, electric current is carried by both free electrons and holes. Free electrons and holes travel in opposite directions. For example, if free electrons flow from left to right then the holes will flow from right to left.

How do transistors amplify current?

A transistor acts as an amplifier by raising the strength of a weak signal. The DC bias voltage applied to the emitter base junction, makes it remain in forward biased condition. This forward bias is maintained regardless of the polarity of the signal.

How do transistors work?

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.

How is a PNP transistor connected in a circuit?

First of all, to turn on the PNP transistor, you need the voltage on the base to be lower than the emitter. For a simple circuit like this, it’s common to connect the emitter to the plus from your power source. This way, you know what voltage you have on the emitter.

What are the applications of PNP transistor?

PNP Transistor Applications. 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. i.e. emergency shutdown. Used in Darlington pair circuits.

How do you calculate the output of a PNP transistor?

I C = β I B + (1+ β) I CBO. The output characteristics of PNP transistor are same as NPN transistor characteristics. The small difference is that the PNP transistor characteristic curve rotates 180 0 to calculate the reverse polarity voltages and current values.

What is the current source of a transistor?

The current source operates because of the fact that the collector current in a transistor circuit is Β times the base current. This is independent of the collector voltage, provided that there is sufficient voltage to drive the current through the load device in the collector. Single transistor active current source

What is the use of PNP transistor in Darlington pair circuit?

PNP Transistors are widely used in Darlington pair circuits. They are used as switches. They are used as oscillators. PNP Transistors are used to source current. Makes the circuit design simpler as it generates signal referenced to negative power supply rail.