In this tutorial, we are going to learn about what is Rectifiers & Linear IC’s?
Rectifiers – The PN junction is rectifier because it is use to convert AC into DC.
PN – Junction:-
SI, is a member of group IV of the periodic table of elements, that is having four electrons per atom in its outer orbit. A pure Si material is known as an intrinsic semiconductor with resistivity that is too low to be an insulator & too high to be a conductor. It has high resistivity of an intrinsic semiconductor sits charge counters that are available for conduction of specific impurities.
The process of adding impurities is called doping, which is a single atom of the added impurity per over a million silicon atoms. With different impurities, levels & shapes of doping, high technology & packaging, the finished power devices are produced from various structures of in type & p-type semiconductor layers.
N-type Material: –
If pure Si, is doped with a small amount of a group V element, such as phosphorus, arsenic, each atom of the doping from a covalent bond within the Si lattice, leaving a loose. This loose e greatly the conductivity of the material. When Si, is lightly doped with an impurities such as phosphorus, the doping is denoted as n-doping & the resultant material is referred to as n-type semiconductor.
P-type material: –
If pure Si is doped with a small amount of group III element, such as boron, gallium or Indian, a vacant location called a hole introduced into the Si cattier. Analogous to one, a hot can be considered a mobile charge cattier as it can be filled by an adjacent, which in this way leaves a hot behind. These holes greatly increase the conductivity of the material. When the Si, is lightly doped with an impurities such as boron, the doping is denoted as P-typing & the resultant material is referred to as a p-type semiconductor. Therefore, there are freeing available in an n-type material & free holes available in a p-type material.
- In p-type – holes – majority carriers
- E – majority carriers
- N- Type e –majority carriers.
- Holes – majority carriers.
These carriers are continuously generated by thermal agitations, they continue & recombine in accordance to their life time & they achieve an equilibrium density of carriers from about 10\10 to 10\3 cm3 over range of about 0c to 1000c. Thus, an applied electric field can cause a current flow in an n-type or p-type material.
A p-n junction is the metallurgical boundary b/w n-&p- regions a semiconductor crystal A junction can’t be found by simply pressing the pieces of p & n-type semiconductor together. Such an arrangement, impact, will produce discontinues in the regular crystal total and will stop the flow of e & holes across the interface. It can be formed by starting with a block of, for example, an n- type semiconductor & converting a part of it to the p type by several methods like alloying, diffusion & epitaxial growth. The p-n-jn is the basic building block of a large number of devices including integrated circuits.
Junction in thermal Equalities:- Let the two regions (n—type &p-type are brought into intimate contact. Since the Hole concentrations is higher on the p-side that n-side, holes different from the p- two they leave behind uncompensated negatively charged acceptations. Similarly, some they charged do not ions near there are left uncompensated as diffuse from the n- side to the p-side. Thus a double layer of charges is formed near the junction having negative space charge on the p-side & a space charge on the n-side.
Since the space charge region is depleted of mobile carriers, it is also called the depletion region, the n- & p- regions on the two sides of the depletion region contain no net charge & each of these will be referred to as the natural region. The space charge region creates an electric field that is directed from the charged donor ions to words the negative charge of acceptor ions. This built-in field presents a barrier to the flow of majority carriers but aids the how of majority carriers.
At thermal equilibrium magnitude of built -in field is such that the diffusion of e (holes) is exactly balanced by their drift tendencies & no net current flows across. The electric field in the space charge region cause a potential difference b/w the p- &n- neutral regions. This potential difference is called the built-in voltage.
Application of Bias:-
Applications of an external voltage to the p-n junction are called biasing. Biasing disturbs the balance b/w the diffusions & drift currents of e ( holes ). As a result, a net current how across the junction.
When a positive voltage is applied to the p-side if the voltage applied to the p-side is higher than that of n-side, it is said to be forward biased. The positive charge on the p- contact pushes hole towards the junction. These holes move to the edge of the depletion region & neutralise some of the negatively charged acceptor ions. Similarly flow from the neutral n-region into the depletion region & neutrals a part of the charge of ionized donors. This decrease in the space charge reduce the depletion region with & lovers the potential battier that was opposing the e & holes at thermal equilibrium. This situation allows more example holes to diffuse over the barrier, white the drift current of minority carriers in the opposite direction remains practically unchanged. Thus, net current flows through the junction which becomes appreciable even for small values of forward bias.
The Junction is said to be reverse biased when the p-region is made negative with respect to the n-region. The majority carriers are now pulled away from the edges of the depletion region. Therefore the depletion region widens, & the potential barriers to the flow of majority carrier are increased.
This in the potential barrier reduces the diffusion current of majority carriers, but the drift current of majority carriers will remains almost unaffected. Because the majority carrier’s concentration on both sides of the Junction is low, only a small number of majority carriers can reach the boundaries of the depletion region. As a consequence, the reverse current in a p-n Junction is small &tends to become independent of applied bias.