How many modes BJT works?

The operational mode of the BJT depends on how the junctions between the regions are biased. Since there are two junctions, the emitter-base junction (EBJ) and the collector-base junction (CBJ), and each of these junctions may be either forward- or reverse-biased, there are four possible modes of operation.

Why BJT is called bipolar device?

Simply put, a BJT is a three-terminal semiconductor device. The name “bipolar” comes from the fact that this type of transistor contains two types of semiconductor material—one positive type (p-type) and one negative type (n-type)—through which a current flows. Bipolar junction transistors usually contain silicon.

What is the reverse active biasing of a bipolar transistor?

By reversing the biasing conditions of the forward-active region, a bipolar transistor goes into reverse-active mode. In this mode, the emitter and collector regions switch roles. In cut-off, biasing conditions opposite of saturation (both junctions reverse biased) are present.

What are BJTs used for?

Bipolar junction transistors (Also known as BJTs) can be used as an amplifier, filter, rectifier, oscillator, or even a switch, which we cover an example in the first section. The transistor will operate as an amplifier or other linear circuit if the transistor is biased into the linear region.

How do you calculate BJT mode?

To find out which mode a PNP transistor is in, reverse all of the < and > signs. For example, to put a PNP into saturation VC and VE must be higher than VB. You pull the base low to turn the PNP on, and make it higher than the collector and emitter to turn it off.

What is the symbol of BJT?

The basic symbols of BJT are n-type and p-type. Electronic current is conducted by both free electrons and holes in bipolar junction transistor.

What are the two types of BJT?

A bipolar transistor (bipolar junction transistor: BJT) consists of three semiconductor regions forming two junctions. There are two types of structure: npn and pnp.

Which device is bipolar?

A bipolar transistor is a semiconductor device commonly used for amplification. The device can amplify analog or digital signals. It can also switch DC or function as an oscillator. Physically, a bipolar transistor amplifies current, but it can be connected in circuits designed to amplify voltage or power.

Why reverse active mode is not useful?

Just as saturation is the opposite of cutoff, reverse active mode is the opposite of active mode. A transistor in reverse active mode conducts, even amplifies, but current flows in the opposite direction, from emitter to collector. The downside to reverse active mode is the β (βR in this case) is much smaller.

What happens if you put a transistor in backwards?

Yes current can flow in both directions. An NPN transistor backwards is also an NPN. There will still be a reverse beta, however, the backwards NPN transistor won’t work as well as a correctly oriented one will. It’s not recommended.

Can a transistor be used as a switch?

One of the most fundamental applications of a transistor is using it to control the flow of power to another part of the circuit — using it as an electric switch. Driving it in either cutoff or saturation mode, the transistor can create the binary on/off effect of a switch.

What are the three modes of transistor?

Operation Modes

• Saturation — The transistor acts like a short circuit.
• Cut-off — The transistor acts like an open circuit.
• Active — The current from collector to emitter is proportional to the current flowing into the base.