![]() In this case, the holes are the majority carriers, while the electrons are the minority carriers. ![]() ![]() In a p-type semiconductor, current is largely carried by the holes, which outnumber the free electrons. Notice that the material as a whole remains electrically neutral. An excess hole is now present.īecause an acceptor donates excess holes, which are considered to be positively charged, a semiconductor that has been doped with an acceptor is called a p-type semiconductor "p" stands for positive. Since holes will "accept" free electrons, a Group 3 impurity is also called an acceptor.Ī semiconductor doped with an acceptor. This impurity will only be able to contribute three valence electrons to the lattice, therefore leaving one excess hole (see figure below). Now, if one of the atoms in the semiconductor lattice is replaced by an element with three valence electrons, such as a Group 3 element like Boron (B) or Gallium (Ga), the electron-hole balance will be changed. Note each +4 ion is surrounded by four electrons. The variable resistance is provided by using a transistor which is controlled by the amplifier feedback loop. In order to maintain a constant output voltage, the internal resistance can be varied. Since there are no excess electrons or holes In this case, the number of electrons and holes present at any given time will always be equal.Īn intrinsic semiconductor. The transistor stays in an active region or ohmic region or linear region of its operation during the voltage regulation. Each ionic core, consisting of the nucleus and non-valent electrons, has a net charge of +4, and is surrounded by 4 valence electrons. In a pure (intrinsic) Si or Ge semiconductor, each nucleus uses its four valence electrons to form four covalent bonds with its neighbors (see figure below). ![]()
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