3. PLAN DE MARKETING INTERNACIONAL
3.4 Estrategias de promoción
3.4.1 Estrategias de marketing digital y uso del e-commerce
An ideal LC circuit consists of an ideal capacitor (infinite dc resistance) of capacitance
connected with an ideal inductor (zero dc resistance) of inductance . If the capacitor is initially charged with a certain electric charge, upon connecting the inductor to its terminals, an alternative current (ac) will start flowing through the circuit. The resonance frequency of oscillations is dependent on the and values with an amplitude dictated by the total electric charge in the circuit. Considering that frequency measurements are amongst the most precise, with typical frequency counters nowadays being able to detect changes as small as 0.001 ppb in a second, having a measurement technique that can relate physical properties of materials to a frequency value is invaluable. In the practical implementation of LC circuits however, the finite resistance of the inductor and connections are responsible for energy losses in which case the amplitude of current oscillations will be exponentially damped with a time constant dependent of the resistance of the circuit. To keep a steady resonant state in an LC tank circuit, all the energy lost during each oscillation must be replaced and the amplitude of these oscillations must be mainianted at a constant level meaning that the amount of energy replaced must be equal to the energy lost during each cycle. One way of achieving this is taking a part of the output signal, amplifying it and feeding it back to the oscillator. Based on this principle there are a number of LC oscillator types like the Hartley oscillator or the Colpitts oscillator, each with its advantages and drawbacks. Another way of maintaining steady oscillations in a real LC circuit is by compensating for the lost energy using the negative resistance of a tunnel diode (Esaki diode).
A tunnel diode is a semiconductor device based on the quantum tunneling effect of electrons. Reona (Leo) Asaki working for Sony in 1958 discovered the effect in solids reporting that narrow (15 nm) p-n germanium junctions exhibit a region of negative differential resistance characterized by an increase in voltage as the current is decreased [116]. For his finding Asaki received the Nobel prize in Physics in 1973 together with Ivar Giaever "for their experimental discoveries regarding tunneling phenomena in semiconductors and superconductors, respectively" and with Brian David Josephson "for his theoretical predictions of the properties of a supercurrent through a tunnel barrier, in particular those phenomena which are generally known as the Josephson effects". At the time of its discovery, the tunnel diode was one of the most significant electronic devices to emerge since the transistor. Their simplicity,
high switching speeds and extremely low power consumption made them extremely advantageous compared to the transistors or electron tubes in high frequency applications. Tunnel diodes were first manufactured by Sony in 1957 followed by General Electric, Siemens and a number of other companies later. Today, however, are made in relatively low volumes as some of their qualities have been surpassed by other semiconducting devices for most technological application purposes. They are usually made from germanium, but can also be made from gallium arsenide and silicon materials. In a conventional normal junction semiconductor diode, conduction takes place while the lightly doped p-n junction is forward biased and blocks current flow when the junction is reverse biased. This occurs up to a point known as the “reverse breakdown voltage” when conduction begins (often accompanied by destruction of the device). In a tunnel diode, a very narrow p-n junction (nanometers) is heavily doped (thousands times greater than regular diodes) which results in a broken band gap where the electron conduction band on the n side is aligned with the hole valence band on the p side. The conduction and valence band electrons can then tunnel in both directions for zero applied voltage where the tunneling phenomenon is exponentially dependent on the electric field intensity across the barrier. The typical current-voltage (IV) curve of a forward biased tunnel diode is depicted in Fig. 3.1 below.
Figure 3.1 The characteristic I-V curve of a forward biased tunnel diode showing the negative differential resistance region B.
As a forward bias voltage is applied, the relative misalignment of the energy levels is increased and the tunneling of electrons for the n to the p type side creates a forward bias current (region A in Fig.
3.1). Increasing the forward bias voltage value will lead to a maximum tunneling current when the energy of the majority of electrons in the n-region is equal to that of the empty states (holes) in the valence band of p-region. As the forward bias continues to increase, the number of electrons in the n side that are directly opposite to the empty states in the valence band (in terms of their energy) decrease. Therefore decrease in the tunneling current will start (region B in Fig. 3.1). This current voltage relationship accounts for the negative differential resistance region of the I-V curve. As the voltage is further increased, tunneling stops and the junction behaves as for a regular diode (region C in Fig. 3.1).