When exposed to external heat and light, its electrical conductivity changes significantly.

Doping certain impurities into a pure semiconductor will significantly change its conductivity

At absolute 0 degrees (T=0K) and without external excitation, the valence electrons are completely bound by covalent bonds, and there are no freely moving charged particles (i.e. carriers) in the intrinsic semiconductor, which is equivalent to an insulator.

At normal temperature, due to thermal excitation, some valence electrons gain enough energy to escape from the constraints of the covalent bond and become free electrons, while leaving a vacancy on the covalent bond, called a hole.

The electron current formed by the directional movement of free electrons.

The valence electrons bound by the nucleus fill holes in a certain direction, forming a hole current.

complex

The higher the temperature, the greater the thermal motion, the more free electrons and holes, the higher the concentration of carriers, and the stronger the conductivity of the intrinsic semiconductor.

The electrons provided by the pentavalent element make the pentavalent element become a positive ion with the same concentration as the pentavalent element atom.

Holes generated by intrinsic semiconductors

The holes provided by trivalent elements accept electrons and become charged negative ions. The concentration is related to the doping concentration.

Free electrons generated by intrinsic semiconductors

The internal electric field is weakened and multi-sub diffusion is strengthened, which can form a larger forward current.

thinning of space charge region

When a forward voltage is applied, the PN junction is in a conductive state, showing low resistance, and the forward current is large.

The internal electric field is strengthened, the diffusion of majority carriers is suppressed, and the drift of minority carriers is strengthened. However, due to the limited number of minority carriers, only a small reverse current can be formed.

The space charge region thickens

When a reverse voltage is applied, the PN junction is in a cut-off state, showing high resistance, and the reverse current is very small.

Silicon tube ~0.5V

Germanium tube ~0.1V

Silicon 0.6~0.8V

Germanium 0.2~0.3V

The maximum forward average current allowed to flow through the diode when the diode is used for a long time. If exceeded, overheating of the PN junction will damage the tube.

The reverse peak voltage given to ensure that the diode is not broken down is generally 1/2 or 2/3 of the reverse breakdown voltage UBR

Refers to the reverse current when the diode is applied with reverse peak operating voltage.

The larger the reverse current is, the worse the unidirectional conductivity of the diode is. Reverse current is affected by temperature. The higher the temperature, the greater the reverse current.

Forward conduction: tube pressure drop

Reverse cutoff: equivalent to disconnection

Forward conduction, reverse cut-off

Operating Voltage

The voltage across the tube when the voltage regulator tube is working normally (reverse breakdown)

The coefficient of voltage stabilization value affected by temperature change, the percentage change in voltage stabilization value caused by every 1°C change in ambient temperature.

The smaller the value, the steeper the curve and the better the voltage stabilization performance.

Maximum stable current

The electrons in the emitter area recombine in the base area to form a current

The emitter junction is forward biased, and electrons in the emitter region continue to diffuse toward the base region, forming an emitter current.

Electrons diffuse and recombine in the base region

Diffusion of holes from the base region to the emitter region can be ignored

Diffusion of most electrons to the collector junction

The collector region collects electrons diffused from the emitter region

The collector junction is reverse biased, and the reverse current formed by minority carriers is greatly affected by temperature.

The electrons that diffuse from the emitter region to the base region and reach the edge of the collector region are pulled into the collector region to form

Ub>Un

Uc>Ub

Positive bias: P N-

Small changes in base current can cause large changes in collector current.

Using a small current change to control a larger current change, a transistor is a current control device.

The emitter junction is forward biased and the collector junction is reverse biased.

When deeply saturated

The emitter and collector are like a switch, and the resistance is very small.

The emitter junction is reverse biased and the collector junction is reverse biased.

The emitter and collector are like a switch open, and the resistance is very large.

The collector junction is reverse biased and the emitter junction is forward biased.

Transistor temperature characteristics are poor