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Just like the Resistor, the Capacitor, sometimes referred to as a Condenser, is a passive device, and one which stores its energy in the form of an electrostatic field producing a potential difference (Static Voltage) across its plates. In its basic form a capacitor consists of two or more parallel conductive (metal) plates that do not touch or are connected but are electrically separated either by air or by some form of insulating material such as paper, mica or ceramic called the Dielectric. The conductive plates of a capacitor can be either square, circular or rectangular, or be of a cylindrical or spherical shape with the shape and construction of a parallel plate capacitor depending on its application and voltage rating.

When used in a direct-current or DC circuit, a capacitor blocks the flow of current through it, but when it is connected to an alternating-current or AC circuit, the current appears to pass straight through it with little or no resistance. If a DC voltage is applied to the capacitors conductive plates, a current flows charging up the plates with electrons giving one plate a positive charge and the other plate an equal and opposite negative charge. This flow of electrons to the plates is known as the Charging Current and continues to flow until the voltage across both plates (and hence the capacitor) is equal to the applied voltage Vc. At this point the capacitor is said to be fully charged with electrons with the strength of this charging current at its maximum when the plates are fully discharged and slowly reduces in value to zero as the plates charge up to a potential difference equal to the applied supply voltage and this is show below.

Tin is a silvery-gray metallic element which has been used by humans for thousands of years. The symbol for tin is Sn, from the Latin stannum, and its atomic number is 50, placing it with other metals such as antimony and aluminum. Almost every continent on Earth has a source of tin, usually in the form of cassiterite, an oxide mineral which contains tin. In addition to the wide range of manufacturing uses for tin, the metal is also nutritionally necessary, albeit in trace amounts.

The word for the metal appears to have been borrowed from a pre-Indo-European language. Old forms of German and Dutch, among other languages, have cognates for the word, but the roots are somewhat unclear. The murky etymology of the word supports research by anthropologists which suggests that humans have been interacting with tin for at least 5,000 years, if not longer.

The term “nucleus” is used in several different ways in the sciences, although all cases reference a critical structure found at the center of something. In fact, the word “nucleus” means “kernel” or “core,” and it comes from an Ancient Greek word meaning “nut.” As a general rule, the nucleus is so critical that the surrounding structure cannot survive without it.

In biology, the nucleus is a small structure located inside the cells of eukaryotic organisms. The cell nucleus is actually one of the defining characteristics of eukaryotes, as the structure allows cells and organisms to reach a very high level of complexity. This structure without the cell contains the organism's DNA, and the nucleus is responsible for regulating gene expression, duplicating DNA as needed, and passing on hereditary traits, in the case of egg and sperm cells.

The atomic number of an element is equal to the number of protons in the nucleus of an atom of the element. Protons are positively charged particles found in the center of every atom. Each element has its own unique number and is differentiated from one another by the number of protons it has. The nucleus of an atom may also be home to neutrons, but the number of neutrons has no bearing on the element’s atomic number. Electrons reside just outside of the nucleus and also have no bearing on the number.

jb Capacitors are encased in a molded epoxy/plastic shell with epoxy fill. Available in Axial Leaded, Rectangular (Style E); Radial Leaded, Rectangular (Style F); and Axial Leaded, Round (Style T).

Capacitors are wrapped in a skin tight plastic tape and then filled with epoxy on the ends. The most economical of the packaging methods. Available in Axial Leaded, Oval (Style W); Axial Leaded, Round (Style R); Radial Leaded, Oval (Style V); and Radial Leaded, Round (Style U). Special terminal configurations and sizes are also available.

The flatband diagram is by far the easiest energy band diagram. The term flatband refers to fact that the energy band diagram of the semiconductor is flat, which implies that no charge exists in the semiconductor. The flatband diagram of an aluminum-silicon dioxide-silicon MOS structure is shown in Figure 6.2.4. Note that a voltage, V_FB, must be applied to obtain this flat band diagram. Indicated on the figure is also the work function of the aluminum gate, F_M, the electron affinity of the oxide, c_oxide, and that of silicon, c, as well as the bandgap energy of silicon, E_g. The bandgap energy of the oxide is quoted in the literature to be between 8 and 9 electron volt. The reader should also realize that the oxide is an amorphous material and the use of semiconductor parameters for such material can justifiably be questioned.

The flatband voltage is obtained when the applied gate voltage equals the workfunction difference between the gate metal and the semiconductor. If there is a fixed charge in the oxide and/or at the oxide-silicon interface, the expression for the flatband voltage must be modified accordingly.
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Figure: Flatband energy diagram of a metal-oxide-semiconductor (MOS) structure consisting of an aluminum metal, silicon dioxide and silicon.

The energy band diagram of an n-MOS capacitor biased in inversion is shown in below Figure. The oxide is modeled as a semiconductor with a very large bandgap and blocks any flow of carriers between the semiconductor and the gate metal. The band bending in the semiconductor is consistent with the presence of a depletion layer. At the semiconductor-oxide interface, the Fermi energy is close to the conduction band edge as expected when a high density of electrons is present. The semiconductor remains in thermal equilibrium even when a voltage is applied to the gate. The presence of an electric field does not automatically lead to a non-equilibrium condition, as was also the case for a p-n diode with zero bias.

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The MOS capacitor consists of a Metal-Oxide-Semiconductor structure as illustrated by Figure 1. Shown is the semiconductor substrate with a thin oxide layer and a top metal contact, referred to as the gate. A second metal layer forms an Ohmic contact to the back of the semiconductor and is called the bulk contact. The structure shown has a p-type substrate. This will refer to as an n-type MOS or nMOS capacitor since the inversion layer - as discussed in section 2 - contains electrons.

To understand the different bias modes of an MOS capacitor we now consider three different bias voltages. One below the flatband voltage, VFB, a second between the flatband voltage and the threshold voltage, VT, and finally one larger than the threshold voltage. These bias regimes are called the accumulation, depletion and inversion mode of operation. These three modes as well as the charge distributions associated with each of them are shown in Figure 2.

Accumulation occurs typically for negative voltages where the negative charge on the gate attracts holes from the substrate to the oxide-semiconductor interface. Depletion occurs for positive voltages. The positive charge on the gate pushes the mobile holes into the substrate. Therefore, the semiconductor is depleted of mobile carriers at the interface and a negative charge, due to the ionized acceptor ions, is left in the space charge region. The voltage separating the accumulation and depletion regime is referred to as the flatband voltage, VFB. Inversion occurs at voltages beyond the threshold voltage. In inversion, there exists a negatively charged inversion layer at the oxide-semiconductor interface in addition to the depletion-layer. This inversion layer is due to the minority carriers that are attracted to the interface by the positive gate voltage.

'SMD' means Surface Mount Device. SMDs are components with small pads instead of leads for their contacts. They are designed for soldering by machine onto specially designed PCBs and are not suitable for educational or hobby circuits constructed on breadboard or stripboard.