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Today, we'll discuss how feedback connections in voltage amplifiers affect output resistance. Can anyone tell me what happens when we connect feedback to an amplifier?
I think it stabilizes the gain?
Exactly! It helps in stabilizing the gain. Now, in an ideal situation, the feedback network has infinite input resistance and zero output resistance. What do you think happens in non-ideal situations?
The resistances could lower the gain, right?
Correct! It modifies the output resistance, leading us to derive new expressions for our systems under various conditions. Let's remember the acronym 'FIRE' for Feedback Input Resistance Effects!
What does 'FIRE' stand for?
'FIRE' reminds us that feedback can change Input Resistance Effects! Remember, in practical circuits, we often deal with finite resistances.
Let’s now focus on source resistance (R_s). Who can explain why we consider source resistance when calculating output resistance?
I guess it's because it affects how much voltage the load receives?
Precisely! The voltage division with source and feedback network resistances modifies the voltage at the input. How do we mathematically express this?
Using KCL and the voltage divider rule!
Well done! The voltage can be expressed as v_in = -βv_x. Now, when we introduce R_s into the expression, we also need to redefine our beta. Can anyone summarize how we do this?
We get a new beta, β' where it's affected by R_s.
Now that we have established the base concepts, let’s look at a non-ideal circuit with an R_s. How does this influence our feedback configuration?
It changes our output resistance, right?
Correct! Output resistance (R_out) now becomes a function of R_s and the original expressions we derived. What about an example where both output and input resistance are finite?
That would involve adding them in a way that highlights how they influence each other!
Exactly! Remember, when dealing with series and parallel configurations, we must carefully analyze how they impact overall circuit performance.
Let’s transition to trans-impedance amplifiers, where the signal flow and feedback differ significantly. What's special about this configuration?
The input is a current and the output is a voltage?
Yes! And this changes how feedback is applied. What can you tell me about the effect of feedback on output resistance in these circuits?
It still modifies the output resistance, but now we're calculating in terms of voltage gain as opposed to current!
Exactly! We often rewrite the output resistance formula as R_out = R_m (1 + βG). Remember 'M-G' for 'Mixing Gain Impact' when analyzing these effects!
Before we wrap up, let’s discuss real-world applications of these circuits. How does feedback apply in practical scenarios?
In audio amplifiers, feedback helps reduce noise and improve sound quality!
Great example! In applications like these, understanding the non-ideal factors becomes crucial. Can anyone think of a situation where neglecting source resistance could cause issues?
If we ignore it, the actual gain could be much lower than expected!
Exactly! Always remember to account for all resistances in your circuit designs for accurate performance.
In a voltage amplifier with a source resistance of 50 ohms, the output voltage diminishes due to voltage division between the source and feedback network.
In a trans-impedance amplifier, when the input current is increased, the output voltage adapts based on the feedback constant multiplied with the gain of the amplifier.
Feedback's the thread, weaves circuits tight; Stabilizing gain, making things right.
Imagine a city with traffic lights. The lights change (feedback) to control the flow of cars (gain) effectively. If the lights malfunction (non-ideal conditions), traffic chaos ensues!
Use the acronym 'FIRE' to remember: Feedback Input Resistance Effects, signifying how feedback influences input resistance performance.
M-G = Mixing Gain Impact, reminds you that changing input/output parameters alters feedback effects.
Term
What does feedback in electronic circuits do?
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Describe output resistance.
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What is source resistance (R_s)?
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What happens under non-ideal circuit conditions?
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A process where a portion of the output signal is fed back to the input to control the gain and stability of a system.
An electronic amplifier that increases the voltage of an input signal while preserving its original form.
The resistance of a device or circuit measured from its output terminal.
The intrinsic resistance seen at the input of an amplifier circuit, which can affect voltage division.
An amplifier that converts an input current to an output voltage.
This section discusses the impact of non-ideal feedback situations on output resistance in electronic circuits.
The content highlights how feedback connections in voltage amplifiers can alter output resistance, focusing on non-ideal situations involving source resistance and additional network resistances. Various configurations are analyzed to deduce practical output resistance expressions.
In electronic circuits, especially those involving feedback systems, it is critical to understand how non-ideal conditions affect performance. This section delves into various configurations of voltage amplifiers, primarily focusing on the impact of feedback connections on output resistance.
Basic Configuration: Initially, an ideal feedback configuration is discussed, where input resistance is infinite, and output resistance is zero. As we introduce practical non-ideal factors, we see changes in these resistances. In voltage amplifiers, the feedback network’s source resistance plays a pivotal role in defining the feedback circuit's output resistance.
Non-Ideal Situations: The section explores how the introduction of a source resistance (R_s) alters the voltage at the input port (applying KCL principles). The proportion of voltage distributed across various impedances in the feedback network leads to a revised relationship involving new beta values (β') and resultant expressions for output resistance.
Other Configurations: More configurations like that of trans-impedance amplifiers and current amplifiers are also addressed. Each case considers non-ideal components' impact on output resistance, ultimately leading to expressions that account for these resistances and their configurations. The effectiveness of these configurations in maintaining manageable output resistance while maintaining the desired gain is critical for engineers.
This topic is essential for understanding real-world applications of feedback in electronic circuits, particularly in designing amplifiers that need to maintain specific performances under varying loads.