Feedback
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Transcript of Feedback
Feedback
Feedback Concepts
Expresion General de Circuitos Retroalimentados
Efectos de la Retroalimentación Negativa
Effect of feedback on (a) the pole location and (b) the frequency response of an amplifier having a single-pole open-loop response.
Bandwidth with Feedback
Gain calculations with feedback are often based on external resistive elements in the circuit. By removing gain calculations away from internal variations of and gm, the gain becomes more stable.
Gain Stability with Feedback
Amplifier Types
1. Voltaje Amplifier 2. Current Amplifier3. Transconductance Amplifier4. Transresistance Amplifier
Axin
Xout
+ -Carga
Rin
Axin
vinXoutVsvin
+ -
Rout
Amplificador de Voltaje Real
+ -
-Xin
-+
Amplificador de Voltaje Real
Cargavout
Amplificador de Voltaje Ideal
vout+
+ -
Vs
Rs Rs
Xin
Amplificador de Voltaje Ideal
Característica del Puerto de un Amplificador (Variable Voltaje)
Característica del Puerto de un Amplificador (Variable Corriente)
Amplificador de Corriente Ideal
Xin RoutCarga
+ -
Amplificador de Corriente Ideal
Xout
Amplificador de Corriente Real
+ -
RsIs
Axin
Iin=Is
Rout=oo
Is
+
-
Rin=0
Cargavout vout
Xout
Axin
+
-
Rin
Amplificador de Corriente Ideal
Xin
RsIin=Is
Feedback Connection Types
1. Voltaje Amplifier (series–shunt) voltage-mixing voltage-sampling topology.
2.Current Amplifier (shunt–series) current-mixing current-sampling
topology
3.Transconductance Amplifier (series–series)
voltage-mixing current-sampling topology
4. Transresistance Amplifier (shunt–shunt)
current-mixing voltage-sampling topology
a) Voltage-mixing voltage-sampling (series–shunt) topology.b) Current-mixing current-sampling (shunt–series) topology.c) Voltage-mixing current-sampling (series–series) topology. d) Current-mixing voltage-sampling (shunt–shunt) topology.
The Four Basic Feedback Topologies
(a) Ideal Structure
1. Series-Shunt Feedback Voltaje Amplifier
(b) Equivalent Circuit.
𝑅𝑖𝑓 =𝑅𝑖(1+ 𝐴 𝛽)
1. Series-Shunt Feedback Voltaje Amplifier
Measuring the Output Resistance of the Series-Shunt Feedback Amplifier Rof : Vt/I.
𝑅𝑜𝑓=𝑅𝑜
(1+𝐴 𝛽)
1. Series-Shunt Feedback Voltaje Amplifier
Derivation of the A circuit and circuit for the series–shunt feedback amplifier. (a) Block diagram of a practical series–shunt feedback amplifier. (b) The circuit in (a) with the feedback network represented by its h parameters.
1. Series-Shunt Feedback Voltaje Amplifier
Summary of the rules for finding the A circuit and for the voltage-mixing voltage-sampling case
1. Series-Shunt Feedback (Voltaje amplifier)
1. Series-Shunt Feedback (Voltaje amplifier)
Example 1 Series-Shunt Feedback -Voltaje Amplifier
Example 1 Series-Shunt Feedback -Voltaje Amplifier
2
21f
RRR
β1A
Example 1Series-Shunt Feedback -Voltaje Amplifier
Ganancia del Amplificador retroalimentado Af
Resistencia de entrada real del amplificador
Resistencia de salida real del amplificador
Example 2 Series-Shunt Feedback - Voltaje Amplifier
2. Series-Series FeedbackTransconductanceAmplifier
(a) Ideal Structure (b) Equivalent Circuit.
2. Series-Series Feedback Transconductance Amplifier
Measuring the Output Resistance of the Series-Series Feedback Amplifier Rof : Vt/I.
Derivation of the A circuit and circuit for the series–series feedback amplifier. (a) Block diagram of a practical series–series feedback amplifier. (b) The circuit in (a) with the feedback network represented by its h parameters.
2. Series-Series Feedback Transconductance Amplifier
2. Series-Series Feedback Transconductance Amplifier
Summary of the rules for finding the A circuit and for the voltage-mixing current-sampling (series–series) case
2. Series-Series Feedback transconductance Amplifier
2. Series-Series Feedback transconductance Amplifier
Example 2Series-Series Feedback Transconductance Amplifier
Example 1Series-Series Feedback Transconductance Amplifier
Example 2Series-Series Feedback Transconductance Amplifier
Efeie
fe
Eie
feE
iefef
Rhhh
Rhh)R(1
hhβA1
AVsIoA
Feedback gain (Af):
Some of the output current is directed back in series with the input.
Example using a BJT:
3. Shunt-Shunt Feedback Transresistance Amplifier
Ideal Structure
Block diagram for a practical shunt–shunt feedback amplifier.
3. Shunt-Shunt Feedback Transresistance Amplifier
Summary of the rules for finding the A circuit and for the current-mixing voltage-sampling (Shunt-Shunt ) case.
3. Shunt-Shunt Feedback Transresistance Amplifier
Example 1Shunt-Shunt Feedback Transresistance Amplifier
Example 1Shunt-Shunt Feedback Transresistance Amplifier
The output voltage is fed back in parallel with the input.Example of an op-Amp circuit:
RiRoAf
Feedback gain (Af):
Example 2Shunt-Shunt Feedback Transresistance Amplifier
4. Shunt-Series Feedback Current Amplifier
Ideal Structure
Block diagram for a practical shunt–shunt feedback amplifier.
4. Shunt-Series Feedback Current Amplifier
Summary of the rules for finding the A circuit and for the current-mixing current-sampling (shunt–series) case.
4. Shunt-Series Feedback Current Amplifier
Example 1Shunt-Series Feedback - Current Amplifier
Example 1Shunt-Series Feedback - Current Amplifier
Example 1Shunt-Series Feedback - Current Amplifier
Example 2Shunt-Series Feedback - Current Amplifier
Summary of Each Type of Feedback and the Effects on Impedance
A. Voltage A. CurrentA. Transconductance A. Transresistance
Summary of Each Type of Feedback and the Effects on Gain
A. Voltage A. Transconductance A. Transresistance A. Current