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In this type the resistance varies with the applied voltage or current. Negative resistance vs positive resistance: If the I–V curve has a positive slope (increasing to the right) throughout, it represents a positive resistance. An I–V curve that is nonmonotonic (having peaks and valleys) represents a device which has negative resistance.
In practice, the internal resistance of a battery is dependent on its size, state of charge, chemical properties, age, temperature, and the discharge current. It has an electronic component due to the resistivity of the component materials and an ionic component due to electrochemical factors such as electrolyte conductivity , ion mobility ...
The Shockley equation doesn't model noise (such as Johnson–Nyquist noise from the internal resistance, or shot noise). The Shockley equation is a constant current (steady state) relationship, and thus doesn't account for the diode's transient response , which includes the influence of its internal junction and diffusion capacitance and ...
No physical current source is ideal. For example, no physical current source can operate when applied to an open circuit. There are two characteristics that define a current source in real life. One is its internal resistance and the other is its compliance voltage. The compliance voltage is the maximum voltage that the current source can ...
Internal resistance varies with the age of a battery, but for most commercial batteries the internal resistance is on the order of 1 ohm. When there is a current through a cell, the measured e.m.f. is lower than when there is no current delivered by the cell.
Contact resistance values are typically small (in the microohm to milliohm range). Contact resistance can cause significant voltage drops and heating in circuits with high current. Because contact resistance adds to the intrinsic resistance of the conductors, it can cause significant measurement errors when exact resistance values are needed.
The role of the base resistor is to expand the very small transistor input voltage range (about 0.7 V) to the logical "1" level (about 3.5 V) by converting the input voltage into current. Its resistance is settled by a compromise: it is chosen low enough to saturate the transistor and high enough to obtain high input resistance.
For NPN open collector outputs, the emitter of the NPN transistor is internally connected to ground, [1] so the NPN open collector internally forms either a short-circuit (technically low impedance or "low-Z") connection to the low voltage (which could be ground) when the transistor is switched on, or an open-circuit (technically high impedance ...