Loading the lesson
Loading the lesson
Search AllRounder.ai
Search the courses, subjects, tracks, games and features, or jump straight to a page.
Search the courses, subjects, tracks, games and features, or jump straight to a page.
Learn it your way
A short class with Sarah and her students. The other ways are under More.
Sign up free to listen. Transcripts are free to read.
Today, we will discuss feedback connections in amplifiers, specifically focusing on their impact on output resistance. Can anyone tell me why feedback is important in amplifiers?
Feedback helps stabilize the gain and improve bandwidth.
Exactly! Feedback connections can greatly influence an amplifier's performance. We can categorize feedback in amplifiers, like shunt-series feedback. What do you think this term means?
Isn't it related to how signals are mixed and sampled?
Yes, you are correct. Shunt-series feedback means sampling a voltage in a shunt fashion and applying it in series, affecting the output resistance. Let's review the terms involved.
What are the ideal conditions for feedback connections?
In ideal feedback systems, we assume infinite input resistance and zero output resistance. This simplifies our calculations. Nevertheless, real-world scenarios often introduce finite resistances, making it important to adapt our models.
In summary, feedback can alter the output resistance significantly. Next, we will derive the output resistance mathematically. Remember, R_out and feedback factor β play key roles.
Let's derive the output resistance. When we apply a voltage source to the output and measure the resulting current, we get a relationship defined by R_out. Can someone explain how we proceed?
We need to use Kirchhoff's laws to relate voltage and current.
Correct! We assume the internal voltage as A_v and relate it to the feedback current. Applying the feedback factor β can adjust this relationship. What happens when we have source resistance?
The calculated β changes, impacting the output resistance!
Exactly! The dependence on R_s alters our output resistance calculations, moving beyond the ideal model. These adjustments are essential in practical scenarios.
How do we take into account the finite resistances in the feedback network?
Good question! Each component's resistance alters the feedback factors we calculated. We must consider these resistances in succession, ultimately leading to a more complex yet realistic model.
To recap, understanding the feedback factors and output resistance interplay is vital for designing effective amplifiers.
Now let’s switch to trans-impedance amplifiers. How does this configuration differ from our previous examples?
In trans-impedance amplifiers, we have current input and voltage output, right?
That's correct! In essence, it’s the reverse of what we discussed earlier. What can you say about the feedback mechanisms in this setup?
The feedback types remain the same, but the relationship between input and output signals changes.
Absolutely! The configurations might be similar, but the effects on output resistance vary. How do we derive output resistance in this configuration?
We still measure voltage and current, applying similar principles as in voltage amplifiers.
Exactly! We apply the same understanding, while adjusting for the new signal type. Ensuring clarity here helps solidify your knowledge.
To conclude, remember that feedback inherently influences the amplifier's performance and output resistance.
We define feedback configurations such as shunt-series feedback, highlighting their characteristics and effects on circuits.
An ideal feedback connection assumes infinite input resistance and zero output resistance. However, in practical applications, we consider finite resistances impacting the calculated output resistance.
The output resistance is derived by applying voltage to the output port while observing the resulting current, elucidating the significance of feedback on the output port impedance.
The presence of source resistance modifies the feedback factor β, which in turn affects the overall output resistance.
We also examine trans-impedance amplifiers where the output is in current format and the feedback mechanisms are different, yet the analysis remains conceptually similar.
In conclusion, understanding how feedback connections alter output resistance is crucial for designing efficient analog circuits, with implications for performance and stability.
Feedback flows, both high and low, through amplifiers, it helps us grow.
Imagine a water pump (amplifier) where feedback (a sensor) keeps track of water flow, ensuring needed adjustments for optimal water level.
For Feedback connections: 'FAM' - Feedback, Amplifier, Modify.
RAVEN: Resistance, Amplifier, Voltage, Effects, Network.
Term
What defines the output resistance in an amplifier?
Click to flip
Term
How does shunt-series feedback work?
Click to flip
The resistance seen by the load connected to the output of an amplifier.
A coefficient that quantifies the portion of output used in feedback; influences performance.
An amplifier that converts input current into output voltage.
A feedback configuration where voltage is sampled from a shunt path and applied in series.
An amplifier designed to increase the voltage of a signal at its output.
This section discusses the changes in output resistance resulting from feedback connections in analog voltage amplifiers and trans-conductance amplifiers.
The section delves into the principles of output resistance in voltage amplifiers with feedback connections, exploring both ideal and non-ideal conditions, resistance configurations, and the impact on performance. It also introduces feedback mechanisms in trans-conductance amplifiers, elaborating on how output resistance is affected in these scenarios.
In this section, we explore the concept of output resistance in the context of feedback connections applied in analog voltage amplifiers. Specifically, we begin with voltage amplifiers and how feedback influences their output resistance.
Feedback Connection Types: We define feedback configurations such as shunt-series feedback, highlighting their characteristics and effects on circuits.
Ideal vs Non-Ideal Feedback: An ideal feedback connection assumes infinite input resistance and zero output resistance. However, in practical applications, we consider finite resistances impacting the calculated output resistance.
Output Resistance Definition: The output resistance is derived by applying voltage to the output port while observing the resulting current, elucidating the significance of feedback on the output port impedance.
Effects of Source Resistance: The presence of source resistance modifies the feedback factor β, which in turn affects the overall output resistance.
Trans-impedance Amplifiers: We also examine trans-impedance amplifiers where the output is in current format and the feedback mechanisms are different, yet the analysis remains conceptually similar.
In conclusion, understanding how feedback connections alter output resistance is crucial for designing efficient analog circuits, with implications for performance and stability.