- #1
DaTario
- 1,056
- 42
Hi all,
I would like to know how pn junction work?
thanks
DaTario
I would like to know how pn junction work?
thanks
DaTario
DaTario said:If all atoms are electrically neutral, why electrons from the donor type go to the acceptor side?
DaTario
DaTario said:Why this migration stops? Does it have to do with temperature in some sense?
DaTario
DaTario said:I don´t understand the energy level diagram. Neither before the migration nor after, when the potential forms a smooth curve between the junction.
DaTario
DaTario said:Do holes produce current? How so?
DaTario
LydiaAC said:Since the built-in electric field push electrons from P-side to N-side, an electron in the P-side has more energy than an electron in the N-side in the same way as a book on the table has more energy than a book on the floor. Thereby, you must draw the energy level in P-side higher than in the N-side. In the transition zone, the connecting curve is actually smooth, but their exact shape is something complicated. You will not lost anything relevant drawing it as a line. To work with holes, you must have a lot of imagination since they need more energy for staying in the N-side than for staying in the P-side. I solve this problem, putting my book head down.
Not OK.DaTario said:P-side has lot of holes. So, outer electrons feel higher attractive forces to this network of atoms than in the N-side. Ok1 ?
Not OK.DaTario said:Positive carriers (whatever they are) will consequently experience more attractive forces in the N-side, Ok2 ?
Not OKDaTario said:Electric potential is usually higher near positive charges, but electric energy is a different concept, and must be higher near repulsive regions. Therefore, the energy diagram which puts P-side higher than the N-side (both valence and conduction band) must be related specifically to positive charges, Ok3 ?
Not OK.DaTario said:Finally for the moment, if we would like to write an energy diagram for the electron, the situation would be the opposite, i.e., P-side would be lower than the N-side, Ok4 ?
DaTario said:Although N-type has more electrons than holes at the beginning of the junction, it is the diffusion process that allows for a positive charge to build up in this region, the converse applying to the P-side, Ok5 ?
DaTario said:You said that the local charge in both types of semiconductors travels through the bulk because these charges are created by thermal effects that promote either valence electrons to holes or electrons in the donor's level "Ed" to the conduction band. Is it Ok6 ?
LydiaAC said:Creating electrons or holes, never alter global charge but it can change dramatically the number of "free charges" or "carriers", that is, charge that can move.
By thermal processes, you are obliged to create electrons and holes by pairs.
You cannot get a P or N semiconductor only with thermal processes.
Impurities allows you to create electrons without creating holes, or holes without creating electrons.
Diodes work by allowing current to flow in only one direction. They have a pn junction, which is the interface between a p-type and n-type semiconductor. The p-type has an excess of positive charge carriers (holes) while the n-type has an excess of negative charge carriers (electrons). When a voltage is applied in the forward direction, the majority charge carriers are able to move across the junction, creating a current. However, in the reverse direction, the majority carriers are unable to cross the junction, resulting in a very small current or no current at all.
The main purpose of a diode is to act as a one-way valve for electrical current. It is commonly used in circuits to convert alternating current (AC) to direct current (DC), which is necessary for many electronic devices to function properly. Diodes also have other applications such as voltage regulation, signal demodulation, and protection against reverse polarity.
A diode is fundamentally different from a resistor because it exhibits non-linear behavior when a voltage is applied. This means that its resistance changes based on the voltage across it. In contrast, a resistor has a constant resistance regardless of the applied voltage. Additionally, a diode only allows current to flow in one direction, while a resistor allows current to flow in both directions.
The symbol for a diode in a circuit diagram is a triangle with a horizontal line at the tip and a vertical line connected to the base. The horizontal line represents the anode (positive terminal) and the vertical line represents the cathode (negative terminal). This symbol is used to indicate the direction of current flow through the diode.
Temperature can affect the performance of a diode in several ways. One major effect is that the reverse current (current flowing in the reverse direction) increases with temperature. This is due to the increase in the number of thermally generated minority charge carriers at the pn junction. Additionally, the forward voltage drop of a diode decreases with increasing temperature, which can affect its voltage regulation capabilities. Therefore, it is important to consider temperature when designing circuits with diodes.