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1.0
Gain, input/output impedance, frequency response, noise, linearity
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4 types of feedback
Voltage-series
Current-series
Voltage-shunt
Current-shunt
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Feedback Amplifier Types
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Voltage-Series Feedback
Vo = A*Vi = A(Vs Vf) = A*Vs A*Vf = A*Vs A(A)Vo
(1 + A)Vo = A*Vs
Vo/Vs = A/(1 + A)
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Voltage-Series Voltage-Shunt Current-Series Current-Shunt
Gain w/o A Vo/Vi Vo/Ii Io/Vi Io/Ii
Feedback Vf/Vo If/Vo Vf/Io If/Io
Gain with Af Vo/Vs Vo/Is Io/Vs Io/Is
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Vo/Vs = A/(1 + A*Bf)
Voltage-Series with input and output resistances
Voltage-series feedback - Avf, Zif, Zof
Avf = Vo/Vs
Vo = A*Vi
Vi = Vs Bf*Vo
Vo = A*(Vs Bf*Vo)
Vo(1 + A*Bf) = A*Vs
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Vs Vi Bf*Vo = 0
Vi = Is*Zi
Vo = A*Vi
so,
Vs Is*Zi Bf*A*Is*Zi = 0
Vs/Is = Zi(1 + Bf*A)
Zof
Disconnect RL and replace with Vx
Zof = Vx/Ix
Vx = Ix*Zo + A*Vi
Vi = -Vf = -B*Vx
Vx = Ix*Zo + A(-B*Vx)
Vx(1 + BA) = Ix*Zo
Zof = Vx/Ix = Zo/(1 + BA)
Zif = Vs/Is
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age-Series
Voltage-Series
Volt
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Common-emitter amplifier with an emitter resistor.Current-Series
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Voltage-shunt feedback
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Voltage-Shunt
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eedbackCurrent-series f
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urrent-shunt feedbackC
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Vs = Ii*Zi
Is = Ii + B*Io
= Ii + B*A*Ii
Is = (Vs/Zi)(1 + BA)
Vs/Is = Zi/(1 + BA)
Now disconnect RL and replace with Vx
Realize that Zo is in parallel with the A*Ii = Io source,
Zof = Vx/Ix
Vx = (Io + Ix)*Zo
A*Ii Vx/Zo = Io = - Ix
A*(-B*-Ix) Vx/Zo = -Ix
(B*A + 1)Ix = Vx/Zo
Zf = Vx/Ix = Zo(1 + B*A)
Zif = Vs/Is
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etermine the following,
a) f = 1.44/(RA + 2RB)C
C = 0.16nF
b) T(high) = 1.1RA*C
C = 4.24nF
D
b) This single shot has a pulse width of 35s. RA = 7.5K.
What is the value of the capacitor, C ?a) The frequency of this oscillator is 400 kHz.
What is the value of the capacitor, C ?
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db k d ill i i f
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F db k d O ill t Ci it 28 f 28
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