Threshold voltage

The threshold voltage, also referred to as threshold voltage, the forward voltage and the knee voltage and rare buckling, in the electronics, the voltage applied to a barrier layer of a rectifier or diode voltage, wherein the current is substantially greater than the reverse current.

Possible definitions for the threshold voltage are:

  • The voltage drop across the diode when a current of 1 mA. This is typically done for encoders with built-in diode tester and usually corresponds to the 1 k-ohm range in the resistance measuring range of the instrument.
  • The voltage which can be read from the characteristic diagram, if the seemingly straight line part is extended to the x-axis.

Description

However, the current-voltage characteristic of a barrier layer does not have a characteristic kink or a natural threshold voltage, this is rather a misunderstanding that the coarse scale is created by the representation of the characteristic curve. Rather, the curve is an exponential function and the differential internal resistance becomes higher and higher towards the coordinate origin.

Start the thus determined threshold voltages of germanium signal diodes and Schottky diodes typically at 0.3 V, that of silicon diodes, with typically 0.6 V. For example, a bridge rectifier of silicon diode to a supply voltage of 5 Vrms put under load only an output voltage of about 3.6 VDC available because there are always two diodes are traversed.

Shockley, the equation describes the flow of current through the diode in the pass band and the special case of an Arrhenius equation:

  • Reverse saturation current (short: reverse current ):
  • Emission coefficient:
  • Temperature Voltage: k: Boltzmann 's constant, T: absolute temperature, q: elementary charge; at room temperature.

Notwithstanding, the term forward voltage in the art usually used for the voltage drop across a diode or similar parts in operating condition. For example, a rectifier for an amp is granted, the manufacturer must indicate the voltage for this power and predetermined ambient temperature.

Current–voltage characteristic Boltzmann constant Thermodynamic temperature Ampere
295327
de