[review of analog electricity - diode]

1、 Definition of intrinsic semiconductor

1） semiconductor ： Semiconductors with pure crystal structure are called intrinsic semiconductors ;

2）PN junction ： It has a single conductivity ;

3） Reverse breakdown ： Unidirectional conductivity is lost when the reverse voltage is too high （ See the manual of semiconductor for details ）;

4）PN The capacitance effect of the junction ： When the signal frequency is too high , Loss of unidirectional conductivity .

2、 Semiconductor diode

1） Basic principle of doping in semiconductors “ Trans type ”,N Type semiconductor doped P Type semiconductor , Or vice versa ;

2） There are three types ,1、 Point contact type ： Suitable for high frequency circuit and low power rectifier ;2、 Surface contact type ： Because the junction capacitance is large , Therefore, it is applicable to lower frequency , Generally used as rectifier ;3、 Flat ;

3）N perhaps P On voltage of type a semiconductor , Silicon material Ud=0.7V, Germanium material Ud=0.2V, What you don't usually say , It's made of silicon , therefore Ud=0.7V;

2.1 Analysis of circuits with diodes

1） Determine which equivalent model to use 3

If a positive pressure drop is given = Constant voltage source model ;

If the positive pressure drop is ignored = Ideal diode , It's like a wire ;

2） Judge whether the diode is on or off

The method is to remove the diode , Calculate the positive voltage Up And negative voltage Un：

For the constant pressure source model , If Up-Un>Ud, For conduction ; If Up-Un<Ud, As of ;

For the ideal diode model , If Up-Un>0, For conduction ; If Up-Un<0, As of ;

3） Replace diodes with simple components （ On or off ）

When conducting ： If it is a constant voltage source model , It is equivalent to a voltage source , The size is Ud, The polarity is the same as the original diode ;

When conducting ： If it is an ideal diode , It is equivalent to a wire ;

At the deadline ： Are equivalent to open circuit

3、 Zener diode

structure ： Usually silicon tube Ud=0.7V On voltage , principle ： Working in reverse breakdown area , Need to limit the current .

Steady voltage ：Uz   ; Maximum stable current Izm And minimum steady current Imin.

effect ： During reverse breakdown , Within a certain current range , It can also be said that it is within a certain range of power consumption , The terminal voltage is almost constant , Show voltage stabilizing characteristics .

3、1 Circuit analysis with zener diode

1、 It is usually a constant pressure source model

2、 Judge the positive conduction of the voltage stabilizing tube 、 Reverse cut-off or reverse breakdown

Up-Un>Ud; In the conduction area , It can be replaced by a voltage source , Constant polarity ;

-Uz<(Up-Un)<Ud; In the cut-off area , It's the equivalent of an open circuit ;

Up-Un<-Uz; In the breakdown zone , It can be replaced by a voltage source , The polarity is opposite to the original ;

4、 Special diode

1） Light-emitting diode ： The forward voltage drop is greater than that of ordinary diodes , Milliampere current can emit light ;

2） Varactor diode ： utilize PN Characteristics of junction capacitance changing with applied voltage , Usually work in the cut-off area ;