Characteristics of BJT Amplifier
BJT amplifier working in the three regions which are mentioned below , also Input – output characteristics of the BJT is shown in below figure, where:
AV -> slope of the curve in the active region
VO -> Output voltage of respective input voltage.
In cutoff and saturation region BJT act as the switch and in the Active region BJT as the amplifier.
Active region
In the active region, the signal gets amplified and the phase reverses from 00 (degree) to 1800 (degree). This region is in between active and saturation region. Transistor is operate in this region when collector is reverse and emitter is forward biased.
IC = IB. β
IC -> Collector current.
β -> current amplification factor.
Saturation region
Next region in transistor behave as a close switch. Collector and emitter are sorted. The CE current is maximum in the saturation region.
Here, in this region
IC = IE
IC -> collector current, IE -> emitter current
Cutoff region
In this region transistor behave as a open switch, hence current between collector, emitter and base is zero.
Here ,
IB = IC = IE = 0 (No current flow)
IB -> Base current
IC -> Collector current
IE -> Emitter current
BJT Amplifier
Bipolar Junction Transistors (BJTs) have a long and diverse history of use in the electronics industry. They are used as a switching mechanism and for amplification in a wide range of applications. BJTs are highly sought after in power electronics because of their low turn on/off times, low voltage drop, high power, voltage, and current ratings, as well as their little leakage current when in blocking mode. In power electronics, they are mostly used for switching applications. The biasing conditions of the junctions dictate the three different modes of operation that bipolar junction transistors (BJTs) display: cut-off, active, and saturation.
A semiconductor device with three layers and three terminals that alternate between p-type and n-type layers is called a bipolar junction transistor (BJT). Three terminals in the BJT is the Collector, Base, Emitter. The arrangement of their layers distinguishes NPN and PNP, the two varieties of BJTs. The base of an NPN BJT is built of p-type material, whereas the emitter and collector are made of n-type material. On the other hand, the base of a PNP BJT is constructed of n-type material, while the emitter and collector are composed of p-type material. The collector-base junction (CBJ) and base-emitter junction (BEJ) are the two junctions found in a BJT.
Table of Content
- What is BJT Amplifier?
- Working Principle
- Types
- Characteristics
- BJT Amplifier Formula
- DC Analysis of BJT Amplifier Circuits
- Advantages and Disadvantages of BJT Amplifier
- Application of BJT amplifier