MindMap Gallery Semiconductor transistor
Transistor, whose full name should be semiconductor triode, also known as bipolar transistor and transistor, is a semiconductor device that controls current. Its function is to amplify weak signals into electrical signals with larger amplitudes, and is also used as a contactless switch.
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The ice hockey schedule for the Milano Cortina 2026 Winter Olympics, featuring preliminary rounds, quarterfinals, and medal matches for both men's and women's tournaments from February 5–22. All game times are listed in Eastern Standard Time (EST).
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Semiconductor transistor
structure
Classification
by frequency
low frequency
high frequency
by structure
NPN type:Uc>Ub>Ue
PNP type:Ue>Ub>Uc
Uc: collector; Ub: base; Ue: emitter
by material
germanium tube
silicon tube
by power
small Medium Large
Features
The base area is thin and the doping concentration is low
The impurity concentration in the emitting region is very high
The collector junction is thicker than the emitter junction
working conditions
Internal conditions: The emitter region is highly doped, the base region is low and thin, and the collector junction is thick
External conditions: emitter junction forward biased, collector junction reverse biased
Level three current
Formation: IE: Diffusion of majority carriers to the base region IB: Free electrons recombine with holes in the base region IC: Free electrons collected in the collector region
relation
main relationship
IE=IB IC
IE>IC,IC>IB,IE>IB
The relationship between IC and IB: β=IC/IB, β common emitter DC amplification coefficient
The relationship between IC and IE: α=IC/IE, α is the common base current amplification coefficient
Voltampere characteristics
Volt-ampere characteristic curve
enter
When Uce<1V: the emitter junction is forward biased and the collector junction is forward biased
When UcE≥1V: the emitter junction is forward biased and the collector junction is reverse biased
output
magnification area
Condition: The emitter junction is forward biased and the collector junction is reverse biased.
Features:
Base control current collector, IC=βIB
Silicon tube 0.7V; Germanium tube 0.3V
cutoff area
Conditions: The emitter junction is reverse biased and the collector junction is reverse biased.
Features:
The base current IB=0, the collector IC is small, IC≈IE≈0
Collector and emitter are equivalent to disconnected
saturated zone
Condition: emitter junction is forward biased, collector junction is forward biased
Features:
Uce increases, Ic rises
Saturation voltage: silicon Uces=0.3V, germanium Uces=0.1V
Emitter junction forward bias: silicon 0.7V, germanium 0.3V
amplifying circuit
Fundamental
Essence: The energy of the DC power supply is converted into the energy of the AC signal
Definition: An analog circuit that can amplify weak signals
Classification
According to signal strength
Voltage amplifier circuit
Power amplifier circuit
According to signal frequency
DC amplifier circuit
Low frequency amplifier circuit
High frequency amplifier circuit
According to the device used
tube amplifier circuit
transistor amplifier circuit
field effect transistor amplifier circuit
Integrated operational amplifier circuit
performance
Magnification A
Voltage: Au=uo/ui
Current: Ai=io/ii
Power: Ap=Po/Pi
Input resistance Ri definition: the input terminal looks toward the output terminal
Output resistance Ro definition: the output terminal looks toward the input terminal
Equivalent resistance of amplifier circuit
distortion
nonlinear
Cutoff distortion: causes distortion at the top of the output waveform
Saturation distortion: causing distortion at the bottom of the output waveform
Frequency distortion: capacitance and inductance caused by different frequencies
Composition principle
DC circuit
Amplify the signal to provide energy
The transistor is in amplifying state
coupling capacitor
The input signal can be applied to the emitter junction of the triode
The amplified signal is effectively transmitted to the load
Regulation
DC component: use lb, lc, Ube丶Uce
Instantaneous value of communication component: use ip丶ic、ube丶uce
Valid values of communication components: use Ib, lc, Ube, Uce
Total amount change: use ib, ic丶UBE丶UcE
DC path: AC signal source is set to zero, and the capacitor is open to DC.
AC path: DC voltage source is set to zero; coupling capacitor is considered a short circuit
analyze
static analysis
Estimation method DC load line equation:
Ucc=IbqRb Ubeq
Uce=Vcc-IcRc
Drawing method
Draw a curve according to the equation
Make the output DC load line
Find the Q point of the output curve
The influence of Rb on Q: Ibq=(Ucc-Ube)/Rb
The influence of Rc on Q: Uce=Ucc-IcRc
The effect of Vcc on Q: moving up and down parallel to the original position
Dynamic waveform analysis: ic=Icq ic, Uce=Uceq Uce