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Feedback. Feedback Concepts. Expresion General de Circuitos Retroalimentados . Efectos de la Retroalimentación Negativa. Bandwidth with Feedback. Effect of feedback on (a) the pole location and (b) the frequency response of an amplifier having a single-pole open-loop response.

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Bandwidth with Feedback

Effect of feedback on (a) the pole location and (b) the frequency response of an amplifier having a single-pole open-loop response.


Gain stability with feedback
Gain Stability 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.


Amplifier types
Amplifier Types

  • Voltaje Amplifier

  • Current Amplifier

  • Transconductance Amplifier

  • Transresistance Amplifier




Feedback Connection Types Corriente)

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


The Four Basic Feedback Topologies Corriente)

  • Voltage-mixing voltage-sampling (series–shunt) topology.

  • Current-mixing current-sampling (shunt–series) topology.

  • Voltage-mixing current-sampling (series–series) topology.

  • Current-mixing voltage-sampling (shunt–shunt) topology.


(b) Equivalent Circuit.

(a) Ideal Structure


1 series shunt feedback voltaje amplifier
1. Series-Shunt Feedback Corriente)Voltaje Amplifier

Measuring the Output Resistance of the Series-Shunt Feedback Amplifier Rof : Vt/I.


1 series shunt feedback voltaje amplifier1
1. Series-Shunt Feedback Corriente)Voltaje Amplifier

Derivation of the A circuit and b 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.



Summary of the rules for finding the a circuit and b for the voltage mixing voltage sampling case
Summary of the rules for finding the Corriente)A circuit and b for the voltage-mixing voltage-sampling case

  • Series-Shunt Feedback (Voltaje amplifier)



Example 1 Corriente)

Series-Shunt Feedback -Voltaje Amplifier


Example 1 Corriente)

Series-Shunt Feedback -Voltaje Amplifier


Example 1 series shunt feedback voltaje amplifier
Example 1 Corriente)Series-Shunt Feedback -Voltaje Amplifier





Example 2 series shunt feedback voltaje amplifier
Example 2 Corriente)Series-Shunt Feedback - Voltaje Amplifier


2 series series feedback transconductanceamplifier
2. Series-Series Feedback Corriente)TransconductanceAmplifier

(a) Ideal Structure (b) Equivalent Circuit.


2 series series feedback transconductance amplifier
2 Corriente). Series-Series Feedback Transconductance Amplifier

Measuring the Output Resistance of the Series-Series Feedback Amplifier Rof : Vt/I.


2 series series feedback transconductance amplifier1
2 Corriente). Series-Series Feedback Transconductance Amplifier

Derivation of the A circuit and b 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 amplifier2
2 Corriente). Series-Series Feedback Transconductance Amplifier


2 series series feedback t ransconductance amplifier
2. Series-Series Feedback t Corriente)ransconductance Amplifier

Summary of the rules for finding the A circuit and b for the voltage-mixing current-sampling (series–series) case



Example 2 series series feedback transconductance amplifier
Example 2 Corriente)Series-Series Feedback Transconductance Amplifier


Example 1 series series feedback transconductance amplifier
Example 1 Corriente)Series-Series Feedback Transconductance Amplifier


Example 2 Corriente)Series-Series Feedback Transconductance Amplifier

Some of the output current is directed back in series with the input.

Example using a BJT:

Feedback gain (Af):


3 shunt shunt feedback transresistance amplifier
3. Shunt-Shunt Feedback Corriente)Transresistance Amplifier

Ideal Structure


3 shunt shunt feedback transresistance amplifier1
3. Shunt-Shunt Feedback Corriente)Transresistance Amplifier

Block diagram for a practical shunt–shunt feedback amplifier.


3 shunt shunt feedback transresistance amplifier2
3. Shunt-Shunt Feedback Corriente)Transresistance Amplifier

Summary of the rules for finding the A circuit and b for the current-mixing voltage-sampling (Shunt-Shunt) case.


Example 1 shunt shunt feedback transresistance amplifier
Example 1 Corriente)Shunt-Shunt Feedback Transresistance Amplifier


Example 1 shunt shunt feedback transresistance amplifier1
Example 1 Corriente)Shunt-Shunt Feedback Transresistance Amplifier


Example 2 shunt shunt feedback transresistance amplifier
Example 2 Corriente)Shunt-Shunt Feedback Transresistance Amplifier

The output voltage is fed back in parallel with the input.

Example of an op-Amp circuit:

Feedback gain (Af):


4 shunt series feedback current amplifier
4. Shunt-Series Feedback Corriente)Current Amplifier

Ideal Structure


4 shunt series feedback current amplifier1
4. Shunt-Series Feedback Corriente)Current Amplifier

Block diagram for a practical shunt–shunt feedback amplifier.


4 shunt series feedback current amplifier2
4. Shunt-Series Feedback Corriente)Current Amplifier

Summary of the rules for finding the A circuit and b for the current-mixing current-sampling (shunt–series) case.


Example 1 shunt series feedback current amplifier
Example 1 Corriente)Shunt-Series Feedback - Current Amplifier


Example 1 shunt series feedback current amplifier1
Example 1 Corriente)Shunt-Series Feedback - Current Amplifier


Example 1 shunt series feedback current amplifier2
Example 1 Corriente)Shunt-Series Feedback - Current Amplifier


Example 2 shunt series feedback current amplifier
Example 2 Corriente)Shunt-Series Feedback - Current Amplifier


A. Voltage Corriente)

A. Transconductance

A. Transresistance

A. Current

Summary of Each Type of Feedback and the Effects on Impedance


A. Voltage Corriente)

A. Transconductance

A. Transresistance

A. Current

Summary of Each Type of Feedback and the Effects on Gain


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