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97.1.4. Basic Feedback Models
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Welcome, everyone! Today, we'll be discussing the four primary feedback configurations used in amplifiers. Can anyone name them?
Is it voltage-shunt and current-shunt feedback?
That's correct! We have voltage-shunt, current-shunt, voltage-series, and current-series feedback. Do you know the differences between them?
I think voltage-shunt involves voltage input and current feedback?
Exactly! Remember, 'shunt' configurations take the feedback from the output, while 'series' configurations mix it with the input. Let's use the acronym SC - 'Shunt to Current' and 'Series to Feedback' to remember these types!
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Now, let’s examine how applying feedback impacts amplifier parameters like gain and resistance. What happens to the voltage gain with negative feedback?
Does it reduce the gain?
Correct! Negative feedback reduces the gain. We refer to this as the 'desensitization factor.' Can anyone tell me how this affects input and output resistance?
I think input resistance decreases in shunt configurations?
Exactly! But in voltage-series feedback, it actually increases. Keep this in mind: the effects differ based on configuration. Let's recite ‘In shunt, input drops; in series, it hops!’ for easy recollection.
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Create a free accountMoving on to practical implementations, how do we use feedback in BJT circuits?
I think we apply it to stabilize gain?
Exactly! And it also applies to op-amp circuits like inverting and non-inverting amplifiers. Always remember the objective is to stabilize performance. Can any of you list some guidelines for selecting components?
Ensure the feedback network's resistance is greater than the amplifier’s input resistance.
Yes! A good rule of thumb. Let’s remember this with 'High to Thrive' - the feedback strength should exceed the input for effective control!
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Create a free accountTo close our session, how do we select the right feedback configuration? What factors should we consider?
We need to know what parameter we want to stabilize!
Very good! Stabilizing parameters like current gain or voltage depends on your objectives. Remember, every configuration brings different consequences. Can anyone summarize?
In summary, we choose based on stability needs, and remember to check for voltage and current!
Perfect! 'Select with Care, Parameter Always aware!' can be our motto for this topic.
Overview
Short Summary
This section introduces feedback models used in analog electronic circuits, focusing on their application in amplifier circuits.
Medium Summary
The section details the basic feedback configurations used in both BJT and op-amp based amplifier circuits. It explores the characteristics, frequency response effects, and practical implementations of feedback systems, aiming to stabilize various amplifier parameters.
Detailed Summary
Detailed Summary
In this section of the course on Analog Electronic Circuits, the focus is on Basic Feedback Models, which are essential for understanding the stability and performance of amplifiers. Feedback can significantly affect the behavior of amplifiers, and this section aims to provide insights into practical applications of feedback configurations.
Key Points Covered:
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Feedback Configurations: The section discusses four main configurations:
- Voltage-Shunt Feedback (or Shunt-Shunt)
- Current-Shunt Feedback (or Series-Shunt)
- Voltage-Series Feedback (Shunt-Series)
- Current-Series Feedback (Series-Series)
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Impact on Amplifier Parameters: It elucidates the modifications in amplifier parameters like voltage gain, input resistance, and output resistance when feedback is applied. The essential takeaway is that negative feedback typically desensitizes the amplifier, thus stabilizing its gain and improving linearity.
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Practical Implementation: It emphasizes how to implement feedback in BJT circuits and op-amp circuits, like inverting amplifiers, integrators, and differentiators. The section also introduces the significance of circuit design considerations for feedback networks, especially focusing on maintaining desired performance through appropriate selection of feedback components.
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Guidelines and Recommendations: Lastly, the section provides guidelines on selecting feedback configurations based on the desired stability and performance objectives. It highlights the importance of understanding the loading effects of feedback networks and the conditions necessary for optimal performance.
Reference YouTube Videos
Audio Book
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Create a free accountHere we have four different configurations, so the names of those configurations are given here; namely voltage-shunt, current-shunt, voltage-series, and current-series or you may say shunt-shunt, series-shunt, and then shunt-series and series-series.
Detailed Explanation
In electronic circuits, feedback configurations are essential for determining how amplifiers behave. There are four main types of feedback configurations: voltage-shunt, current-shunt, voltage-series, and current-series. Each configuration offers a unique way to process signals and influences the amplifier's performance characteristics. The choice of configuration largely depends on what aspect of the circuit one wants to stabilize or control.
Examples & Analogies
Think of feedback configurations like different routes you can take to reach a destination. Each route can lead you to your goal, just as each feedback configuration can help achieve a specific performance in an amplifier. Choosing the right route—whether it's a short direct path or a longer scenic route—depends on your priorities, similar to selecting a feedback configuration based on the desired amplifier characteristics.
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Create a free accountHere we do have the basic model of the feedback system ‒ve feedback system. The input either we may call this is the primary input or just by observing this input we can tell what kind of amplifier we do have or rather this the input type and the output signal type it will decide what kind of amplifier we do have.
Detailed Explanation
A feedback system model allows the analysis of how input and output signals interact in an amplifier circuit. In negative feedback systems, the input signal's characteristics combined with the feedback signal influence the amplifier's behavior significantly. The type of input signals (current or voltage) plays a crucial role in defining what type of amplifier will be implemented, guiding designers on how to stabilize performance.
Examples & Analogies
Imagine you're in a restaurant and the chef asks for customer feedback on your meal. The feedback (like the signal) influences the chef's cooking process for future dishes. Similarly, in a feedback system, the input (customer preferences) affects the output (meal quality), and the overall process optimizes the taste of future meals.
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Create a free accountOnce we are deploying the ‒ve feedback system, according to this formula the main the forward amplifier gain A is getting reduced by this factor, which is referred to as a desensitizing factor (1 + βA).
Detailed Explanation
When negative feedback is applied to an amplifier, its gain (A) is reduced. This reduction is quantified by a desensitization factor, which includes both the feedback factor (β) and the amplifier gain (A). The multiplication of these parameters indicates how feedback stabilizes amplifier gain, allowing it to remain constant under varying conditions.
Examples & Analogies
Consider a thermostat controlling the temperature in a room. As the temperature deviates from the desired set point, the thermostat adjusts the heater's output to bring the temperature back to that set point. Similarly, feedback in an amplifier acts like a thermostat, adjusting the gain to keep it stable, even when external conditions vary.
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Create a free accountDepending on which parameter you would like to stabilize, the feedback configuration can be selected accordingly. For example, if we want to stabilize voltage gain, then we should be selecting the corresponding configuration.
Detailed Explanation
The selection of the feedback configuration is critical because it directly relates to which amplifier parameter (current gain, voltage gain, transconductance) needs stabilization. Designers must be clear about their objective to select the most appropriate feedback configuration effectively. This targeted selection can lead to improved circuit performance and reliability.
Examples & Analogies
Choosing a feedback configuration is like deciding on a skill to improve in sports, such as shooting accuracy in basketball. If the player wants to enhance shooting precision, they'll focus on shooting drills rather than defensive tactics, directing their training efforts towards a specific goal—just like selecting a feedback configuration to stabilize a specific amplifier parameter.
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Key Concepts
Core takeaways and short definitions to help you quickly recall the key ideas from this section.
Feedback Configurations: Different feedback configurations include voltage-shunt, current-shunt, voltage-series, and current-series, each having unique effects on gain and resistance.
Desensitization Factor: A key aspect of feedback is the desensitization of amplifier gain, which stabilizes performance.
Stability Selection: Choosing the appropriate feedback configuration is crucial for ensuring stability and desired performance parameters.
Examples
Step-by-step examples to apply the section's ideas and test your understanding.
An application of voltage-shunt feedback can stabilize the voltage gain of a common emitter amplifier.
Inverting amplifiers utilize feedback to control the output voltage based on the input voltage while maintaining stability.
Memory Aids
Interactive tools to help you remember key concepts
Stories
Memory Tools
Flash Cards
Glossary
Feedback
The process of returning a portion of the output signal to the input to control the behavior and performance of a system.
BJT
Bipolar Junction Transistor, a type of transistor that uses both electron and hole charge carriers.
Voltage Gain
The ratio of the output voltage to the input voltage in an amplifier.
Input Resistance
The resistance seen by the input source of the amplifier.
Output Resistance
The resistance seen by the load connected to the amplifier output.
Desensitization Factor
A factor that reduces the gain of the amplifier when feedback is applied.