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Basic electronics
Published in Raymond F. Gardner, Introduction to Plant Automation and Controls, 2020
Figure 3.4 shows a diode characteristic curve. With forward-bias polarity, the diode conducts well, having very little voltage drop. The forward-biased voltage drop depends on the crystalline base material used. When the diode is made from germanium, the diode forward-bias voltage drop is 0.3V and when it is made from silicon, the voltage drop is 0.7V. In the reverse-bias direction, the diode has the characteristic where it does not conduct, except for very small amounts of leakage current, until the applied voltage becomes large. The point where the diode conducts in the reverse-bias direction is the breakdown voltage. A diode is selected so that the applied reverse-bias voltage is below the breakdown voltage, and it is intended to conduct only in the forward-bias direction. Exceeding the reverse voltage breakdown point will damage conventional diodes.
Thermal Distribution of Electrons, Holes, and Ions in Solids
Published in Juan Bisquert, The Physics of Solar Energy Conversion, 2020
When we apply a bias voltage departing from the zero bias situations, different and asymmetric current responses of the device occur depending on the sign of voltage. The reason for the asymmetric behavior of contacts is discussed later, and the main consequence is the characteristic current–voltage curve shown in Figure 5.13. In the direction denoted “forward bias,” the diode produces a large flow of carriers and current increases exponentially, while in “reverse” bias the diode limits the flow into a constant, relatively small current of a value j0, the reverse saturation current. This current density–voltage characteristic can be expressed as j=j0(eqV/kBT−1)
RF Switches
Published in Mike Golio, Commercial Wireless Circuits and Components Handbook, 2018
A pin diode is a nonlinear device fabricated from a p+nn+ structure, as shown in Fig. 10.1. These devices are widely used in switch applications such as phase shifters [2] and have properties that result in low loss and high frequency performance. A pin diode can also be optically controlled [6], which is desirable for certain applications. The diode is a pn junction device with a lightly doped or undoped (intrinsic) region located between two highly doped contact regions. The presence of the intrinsic region yields operational characteristics very desirable for switching applications. That is, under reverse bias the intrinsic region produces very high values for breakdown voltage and resistance, thereby providing a good approximation to an “open” switching state. Both the breakdown voltage and off-state resistance are dependent upon the length of the intrinsic region, which is limited in design length only by transittime considerations associated with the frequency of operation. Under forward bias, the conductivity of the intrinsic region is controlled or modulated by the injection of charge from the end regions and the diode conducts current, thereby providing the “on” switching state. The “on” resistance of the diode is controlled by the bias current and in forward bias, the diode has excellent linearity and low distortion.
Understanding multi-domain compact modeling of light-emitting diodes
Published in Cogent Engineering, 2021
Minimum forward voltage required for an LED to be conducted in the forward bias condition is known as the “Knee voltage” or the “Threshold voltage”, represented as in Figure 7. Diode acts as a switch in forward bias condition, with theoretically zero resistance to the flow of forward current from anode to cathode. As seen in Figure 7, on attaining , diode starts to conduct with current increasing exponentially for small changes in as seen in equation (6). In reality some finite resistance is offered by the LED junction for the flow of forward current under forward bias, this is the natural resistance of the LED junction and depends on the material and structure of the junction. The change , beyond is caused by forward current flowing through the resistance of the junction, hence the characteristics beyond have a slope where voltage varies with current. This resistance is known as “average ac resistance” or “bulk resistance”.
Characterization the influences of diodes to piezoelectric energy harvester
Published in International Journal of Smart and Nano Materials, 2018
Ming Yuan, Ziping Cao, Jun Luo
At the forward bias status, the diode can be represented by a barrier potential in series with a low forward resistance . Therefore, the diode’s on-state loss is occurred when large forward current is flown in the circuit. At the blocking reverse bias status, the diode can be represented by an open break in parallel with a large reverse resistance . Therefore, the diode’s blocking loss is generated as small reverse leakage current existing in the circuit. The two status are taken in turn via switching, which corresponds to the diode’s switching loss.