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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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