Adel S.Sedra微电子电路期中复习PPT

集电结
collector 集电极 c
集电区 基区 发射区
Three terminals
emitter (E) base (B) collector (C)
N P N
base 基极 b
发射结
Two pn junctions:
emitter-base junction (EBJ) collector-base junction (CBJ).
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The T Model
•
These models explicitly show the emitter resistance re rather than the base resistance rπ featured in the hybrid-π model. Microelectronic Circuits SJTU Yang Hua
发射极 e
emitter
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Operation Modes
Depending on the bias condition (forward or reverse) of each of the two junctions, there are different modes of operation of the BJT. In this course, we are mainly interested in the amplification mode.
Summary of model parameters
(1) Model parameters in terms of DC bias currents: I V V gm = C re = T = α T I VT IE C V V V ro = A rπ = T = β T I IC IB C (2) Model parameters in terms of gm: (3) Model parameters in terms of re:
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Some important results:
A free electron is negative charge and a hole is positive charge. At a steady temperature, the recombination rate is equal to the ionization rate. Carrier concentration in thermal equilibrium
Output Curves for CB Configuration
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The Hybrid-π Model π
• •
The equivalent circuit in (a) represents the BJT as a voltage-controlled current source (a transconductance amplifier), The equivalent circuit in (b) represents the BJT as a current-controlled current source (a current amplifier).
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The Diode Models and applications
Circuit Model
a) b)
Simplified diode model The constant-voltagedrop model Small-signal model Ideal model Zener Diode Model
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Application of the small-signal equivalent circuit-the analysis process
(1)
(2)
(3)

(4)
(5)
Determine the dc operating point of the BJT and in particular the Ic g m = I C , rπ = β , re = VT ≅ 1 VT gm I E gm Calculate the values of the small-signal model parameters: Draw the AC circuit: eliminate the dc source by replacing each dc voltage source with a short circuit and each dc current source with an open circuit Replace the BJT with one of its small-signal equivalent circuit models Analyze the resulting circuit to determine the required quantities, e.g. voltage gain, input resistance and output resistance
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Characteristics of Silicon Junction Diodes
i = I（e s
v
nVT
− 1)
i = I s (e
v
nVT
− 1)
Forward biased Reverse biased
v nVT ≈ I s e − I s
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BJTs
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Physical Structure
Three regions:
emitter region (n type) base region (p type) collector region (n type)
Modes Cutoff Saturation Active EBJ Reverse Forward Forward CBJ Reverse Forward Reverse Application Switching application in digital circuits Amplifier
rd = nVT I DQ , (n = 1,2)
c) d) e)
Modeling the diode Forward characteristic
Modeling the diode Breakdown characteristic
The circuit models are derived from approximating the nonlinear curve into piecewise-line.
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The Content of microelectronic circuits
Devices
Signal generator s 12
Circuits
Analog integrate d circuits 10
Diodes 3
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Basic Concept:
Majority carriers--- Majority carrier is only determined by the impurity, but independent of temperature Minority carriers---only generated by thermal ionization and are strongly affected by temperature .
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Current-voltage Characteristics
Input curve is similar to that of the diode.
iB
iB
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BJTs 4
FETs 5
Basic amplifier s4 5
Differentia l amplifiers 6
Power amplifier s9
Frequency response 7 Microelectronic Circuits
Feedback Analysis 8 SJTU Yang Hua
re =
α
gm
, rπ =
β
gm
1 1 g m = , rπ = (β + 1)re , g m + = re rπ re
(4) Relationships between αandβ :
α
β=
1 α β ,α = , β +1 = 1−α β +1 1−α
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n = p = ni
ni = BT e
2
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3 − EG kT
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Intrinsic Semiconductor(cont’d)