The polarization of the transistor is to switch the glass, which facilitates the passage of the current from the source to the drain, or from the transmitter to the collector. that’s why we use the term “polarization”.
we want to use a transistor to amplify a signal. the transistor is a device with three terminals. he has two junctions. one is the emitter junction and the other is the collector junction. if the two junctions are reverse biased, the transistor is in the off state. if the two junctions are forward biased, the transistor is in saturation. but we want to use the transistor to amplify a signal. for this, the transistor must be in the active region.
Why do we use biasing in transistor?
In the active region, the junction of the transmitter must be forward biased and the junction of the collector must be reverse biased. to properly polarize these two junctions, we need an arrangement of voltage sources and resistors. this arrangement is called a polarization scheme. it is necessary to polarize to place the transistor in the active region so that it amplifies.
transistor is an electronically controlled device. it can be used in two (2) main operating modes, namely
- switching:
- amplification
switching is performed in the cutoff region and the saturation region in bjt, while in the mosfet, switching is performed in the cutting and active region.
The amplification is performed in the active region bjt while in the mosfet in the saturation operation region. to operate a transistor in one of the required modes of operation. transistor need DC bias. otherwise it will not work properly.
a transistor as is is a kind of miniature switch. you apply a little threshold voltage to the base terminal and it lights up, allowing a relatively large current to flow from the collector to the transmitter. Polarization provides quite a configuration based on the components connected to it – capacitors, essentially resistors and other transistors – indeterminately determines the function of the transistor circuit as a whole.
The transistors have the following common polarization configurations: fixed polarization, emitter polarization, voltage divider bias, collector feedback polarization, emitter follower, and common base polarization, such as the type of polarization, which determines whether a transistor circuit becomes an oscillator (in the case of rc oscillator), and oscillation frequency of the oscillator.
A transistor, based on the polarization performed on it, can also serve as amplifiers, relays, transistor switches, constant current sources.
Several polarizations and combinations of these polarized transistors are what you find in logic gates! so transistors are essentially the building blocks of the most complex circuits you can think of, and they are almost useless if they are not biased to provide the function we need!
