Conductive properties: doping properties, thermal properties, photosensitive properties

N-type semiconductor

P-type semiconductor

P-type semiconductors and N-type semiconductors are made on a silicon plate using different processes, and a thin layer with special physical properties is formed at the interface. Stable space charge region, high resistance region, depletion layer

Formation: concentration difference - diffusion movement of multicarriers - magazine ions form a space charge region - the space charge region forms an internal electric field (the internal electric field promotes the drift of minority carriers and prevents the diffusion of multicarriers) - reaches dynamic balance (diffusion current = drift current, the total current is 0)

One-way conductivity

Current equation (not important): Ut=26mV at room temperature

Voltampere characteristics

capacitive effect

Maximum rectified current If: the maximum forward average current allowed to pass through the conductor diode during long-term operation. If it exceeds the limit, it will be easily damaged.

Reverse breakdown voltage Ubr

Maximum reverse working voltage Urm=1/2Ubr

Reverse current Ir: leakage current, saturated leakage current is Is

Maximum operating frequency fm: it takes time for the diode to switch states

Interelectrode capacitance

DC resistance: DC power supply. Rd=Udq/Idq

Microvariable resistance: rd=Ut/Idq (Ut=26mV)

DC model

communication model

Rectifier circuit: converts the input bipolar voltage into a unipolar output. Use ideal models. A diode acts as a switch and conducts electricity in one direction.

Limiting circuit: Use constant voltage drop model. The diode has one-way conductivity and the voltage remains unchanged after conduction. (Analysis method: Find a point to ground; disconnect the diode and analyze the voltage at both ends; then discuss whether it is on or off and the voltage to be found)

Switch circuit: The conduction and cutoff of the diode is equivalent to the on or off of the switch, thereby realizing some logical relationships (analysis method: first assume that it is on or off; discuss the voltage at both ends; whether the assumption is true; find the voltage to be found)

The breakdown state voltage of the voltage regulator tube is constant at Ubr=Uz. During reverse breakdown, when the current changes within a wide range, only a small voltage change is caused.

Application circuit

Photodiode

led