Fundamentals of analog electronic circuits--Basics of semiconductors

I. Basic knowledge of semiconductors

1.1 Eigen Semiconductors
4 valence elements, pure silicon and germanium

1.2 Impurity Semiconductors
N-Type semiconductors: 5 valence elements are incorporated into the intrinsic semiconductor to form redundant electrons
P-Type semiconductors: 3 valence elements are incorporated into the intrinsic semiconductor to form excess holes

Second, Pn Junction

P-type, side n type, form PN junction
The carrier diffusion forms the internal electric field, and the electric field causes the carrier to drift back and strike a balance.

unidirectional conductivity of 2.1 pn junction
The PN Junction Home plus voltage (p positive n negative), the built-in electric field is weakened, the balance is broken, the diffusion is greater than the drift, and the forward current is formed.
id=is*[e^ (U/ut)-1]
is the reverse saturation current (with the reverse voltage current), UT at room temperature of 26mV.

Breakdown of 2.2 pn Junction
Zener Breakdown: <4v (silicon)
Avalanche Breakdown: >7v (silicon)

capacitance effect of 2.3 pn Junction
Barrier capacitance: The space charge caused by the barrier layer
diffusion capacitance: In the forward voltage, the multi-sub in the diffusion process generated by charge accumulation caused by

third, semiconductor diode

3.1 Characteristics of diodes
forward characteristic: silicon tube conduction voltage is 0.6-0.8v, germanium tube is 0.1-0.3v
reverse characteristic: When the reverse voltage is certain, the current is very small, when the reverse voltage exceeds a certain value, the current increases sharply and the breakdown occurs.

3.2 Diode Main parameters
Maximum rectified current if: permissible maximum forward current
maximum reverse operating voltage ur: maximum allowable operating voltage (breakdown voltage)
Reverse Current IR: the current when the reverse voltage is added, the smaller it indicates the better one-way conductivity
maximum operating Frequency FM: Depending on the PN junction capacitance size, the larger the capacitance, the higher the FM
DC Resistance rd: the ratio of DC voltage to DC current at both ends of the tube, non-linearity, the greater the difference between the positive and negative resistance, the better the performance
AC Resistor rd: the ratio of the voltage micro-change to the corresponding micro-current change

3.3 Zener Diode
The reverse voltage changes very little when the diode is working in the reverse breakdown area and the reverse current varies greatly.

Four, semiconductor transistor

   

4.1 amplification of transistors
    Transmit Junction is positive, the transmitting knot multi-sub-diffusion to the base region, the set of electrical junction reverse bias generated reverse electric field, the base of the multi-sub-electric field swept into the collector junction.

Current Distribution Relationship:
Ie=ib+ic
Ic=αie+icbo
Ic=βib+iceo
iceo= (1+β) ICBO
Α=ic/ie
Β=ic/ib

Pole Reverse Current
Iceo: Open base, penetrating current between collector and emitter
ICBO: Open emitter, reverse saturation current of collector junction

4.1 Characteristic curve of transistor

Cut-off zone: Two knots, IB <=0
Saturation zone: Two knots, uce=0.3v
Amplification area: Transmit junction positive Deviation, set electrical junction inverse bias, ic=βib,uce change on the IC has no effect

Fundamentals of analog electronic circuits--Basics of semiconductors