45.4.2 - Behavior Remains Unchanged
Enroll to start learning
You’ve not yet enrolled in this course. Please enroll for free to listen to audio lessons, classroom podcasts and take practice test.
Interactive Audio Lesson
Listen to a student-teacher conversation explaining the topic in a relatable way.
Introduction to Common Collector Amplifier
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Welcome back, students! Today, we are diving into the common collector amplifier. Can anyone tell me why it might be a popular choice in electronic circuits?
I think it's because of its high input resistance.
Exactly! High input resistance means it doesn't load down the previous stage. What about its voltage gain?
It's close to 1, right?
That's right! The gain being nearly 1 makes it useful as a buffer. Remember, we can call this behavior a 'voltage follower.'
Impact of Practical Components
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Let's now analyze how practical components such as R_L affect our amplifier. Who can summarize what we discussed about this last week?
When we discussed ideal conditions, we ignored these components, but now we're looking at them to see their real effects.
Correct! So, if we add R_L, how does that affect our voltage gain?
Isn't it still approximately 1 since R_L is often much larger than other resistances?
Yes! It remains approximately 1 because R_L increases input impedance and maintains output properties.
Source Resistance in Common Collector Stage
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Now let's focus on source resistance, R_s. How do you think it impacts the common collector circuit?
Doesn't it change the voltage applying to the base?
Yes, very good! It causes a voltage drop, which is a crucial consideration.
So, do we still expect the circuit behavior to remain primarily unchanged?
Exactly! Although the voltage at the base is affected, the overall function of the amplifier holds. This stability is key in designing reliable circuits.
Effects of Load Resistance
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Now, how does the output resistance of the common collector amplifier change with an added load resistance, R_c?
I believe R_c in parallel with other resistances may lower the output resistance?
Good observation! However, as long as R_c is not comparable to other resistances, it can still yield high output resistance. How does this align with our earlier discussions?
This aligns with the idea that even in practical situations, if one component dominates, the overall circuit behavior stays similar to the ideal case.
Exactly! Thus far, we see that the common collector amplifier retains its essential functions even with practical modifications.
Conclusion and Review
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
In conclusion, how do practical components affect our common collector and common drain amplifiers?
They lead to minor modifications but don’t fundamentally change the circuit's high input resistance and low output resistance!
And voltage gain stays close to 1!
Precisely! That is the key takeaway from today's session. The main attributes stay intact, ensuring reliability in practice.
Introduction & Overview
Read summaries of the section's main ideas at different levels of detail.
Quick Overview
Standard
This section explores the effects of various resistances in common collector and common drain amplifiers, emphasizing how their fundamental properties, such as voltage gain, input resistance, and output resistance, remain consistent even when practical components are included.
Detailed
In this section, we delve into the operation of common collector (CC) and common drain (CD) amplifiers, particularly how the introduction of realistic circuit components such as resistive loads and source resistances influences their parameters. The voltage gain and input/output resistances of these amplifiers are analyzed under practical conditions. Importantly, it is highlighted that even when these components are integrated, key properties such as high input resistance and near-unity voltage gain are maintained, ensuring that the overall behavior of the circuit remains unchanged. The implications of including source resistance in common collector amplifiers are explored, concluding that the output characteristics remain stable despite its presence. Through careful analysis, we confirm that core amplifier functionality persists, making these circuits reliable in practical applications.
Youtube Videos
Audio Book
Dive deep into the subject with an immersive audiobook experience.
Introduction to Circuit Behavior
Chapter 1 of 5
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
Now, if I consider say source resistance and still if I consider this is 0 then even if I connect the source resistance R , since from this terminal to this terminal, there is no DC path. So, you may say that even if I consider R the behavior of the circuit remains unchanged.
Detailed Explanation
In this part, we are discussing how the introduction of a source resistance (R) does not impact the behavior of the circuit when connected to a specific terminal. It is asserted that there is no direct DC connection between the aforementioned terminals, thus, the overall functionality and response of the circuit remain intact regardless of the presence of this resistance.
Examples & Analogies
Imagine trying to pour water through a pipe with a blockage halfway down; if that part of the pipe (like the source resistance) does not impact the water flow at the opening (the circuit behavior), you can say the water will still flow as if the blockage doesn’t exist - the overall system behaves as intended.
Common Collector Stage Evaluation
Chapter 2 of 5
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
However, if I consider say common collector stage; obviously, there will be the corresponding element here called r . So, it is better to in case if we consider R , then we need to; need to analyze its effect particularly for common collector stage.
Detailed Explanation
In contrast to the previous general case, this section emphasizes the necessity of evaluating circuit behavior in the presence of a source resistance when dealing with a common collector stage. The text indicates that this stage comes with its own intrinsic resistance, namely 'r', which requires careful consideration to understand how it behaves when the source resistance is present.
Examples & Analogies
Think of the common collector stage like a food delivery service. While traffic (the source resistance) might not impede overall service delivery in a clear route, introducing an additional unexpected detour (like the resistance 'r') can change how long it takes for food to arrive, thus requiring a reevaluation of the delivery times.
Analyzing New Parameters with Source Resistance
Chapter 3 of 5
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
So, let us see the common collector amplifier considering this source resistance, signal source resistance. So, we do have the circuit given here. So, we are considering this source resistance R . Again, R we are ignoring, so we are considering one effect at a time.
Detailed Explanation
In this section, the focus shifts to assessing the actual effects of the source resistance on the common collector amplifier. The process begins with visualization of the circuit and noting that only one aspect, the source resistance (R), is analyzed while temporarily ignoring other factors ('R'). This step-by-step approach helps simplify complexities in understanding how the source resistance could affect the circuit characteristics.
Examples & Analogies
Consider a race where runners are allowed to wear only one type of shoe at a time to compare their performance. Similarly, by fixing on source resistance 'R' while ignoring potential complications from other resistances, we can better evaluate its specific impacts on the common collector amplifier's performance, just like running in one shoe helps isolate its effect on speed.
Voltage Gain Implications
Chapter 4 of 5
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
So, if I multiply this with v that gives us the base voltage, and then from the base point to the corresponding collector point the gain it is approximately 1.
Detailed Explanation
This part explains how the voltage gain is affected by the source resistance. When considering the relationship between the input voltage and the output (base voltage) after accounting for the source resistance, the overall gain remains close to one. This indicates that the amplifier allows any signal level to pass through effectively without significant attenuation.
Examples & Analogies
Imagine a sound system where adjusting the equalizer doesn’t significantly change the sounds from speakers. If you turn the dial for bass or treble very slightly but get the same loudness and clarity, that's akin to our condition here: the voltage gain adjusts but retains the same effective output, thus behaving 'approximately' consistently as before.
Current Flowing Through the Circuit
Chapter 5 of 5
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
To get the source resistance sorry the output resistance of this circuit, what you have to do? We need to stimulate the circuit by say v and we need to observe the corresponding current here i.
Detailed Explanation
In this section, the steps for determining the output resistance in the presence of source resistance are described. It involves applying a voltage to stimulate the circuit and measuring the resulting current. This observation will help draw conclusions about how the output resistance behaves when influenced by the source resistance.
Examples & Analogies
Just like testing the flow rate of water from a hose when adjusting the nozzle to see how much pressure changes the flow, similarly, applying voltage here helps unveil how current flows and what resistance levels alter its behavior across the circuit.
Key Concepts
-
Common Collector Amplifier: A configuration that has significant properties like high input resistance and low output resistance.
-
Common Drain Amplifier: Similar characteristics as CC but used in MOSFET technology.
-
Voltage Gain: A critical amplifier parameter, ideally close to 1 for CC and CD amplifiers.
-
Input and Output Resistance: Vital for ensuring minimal loading effects and proper interaction with other components.
Examples & Applications
In practical circuits, R_L is commonly chosen to ensure maximum power transfer while maintaining high input resistance.
In a common collector amplifier used as a buffer, when R_s is increased, the overall function still remains since the voltage drop is negligible.
Memory Aids
Interactive tools to help you remember key concepts
Rhymes
A common collector is quite a keeper, high input resistance, a low output creeper!
Stories
Imagine a water tank (amplifier) where the water level (voltage) remains constant regardless of the input from the hose (source), signifying stability.
Memory Tools
Remember CC: Current and Collector lead to a stable Collector voltage.
Acronyms
RIVe – Remember Input Resistance and Voltage, ensuring reliable output!
Flash Cards
Glossary
- Common Collector Amplifier
An amplifier configuration that provides high input impedance and low output impedance, where the output is taken from the emitter terminal.
- Common Drain Amplifier
Similar to a common collector configuration, but typically implemented with MOSFETs, providing buffering with a low output impedance.
- Voltage Gain
The ratio of output voltage to input voltage in an amplifier, indicating how much the amplifier increases the signal voltage.
- Input Resistance
The resistance looking into the input of the amplifier from a signal source, affecting how much it loads the previous stage.
- Output Resistance
The resistance seen by the load at the output of the amplifier, crucial for determining how the amplifier interacts with connected devices.
- Source Resistance
Resistance at the input of the amplifier which can affect the input voltage and hence modify the voltage gain.
- Load Resistance
Resistance connected between the output and the load, impacting output performance and amplifier behavior.
Reference links
Supplementary resources to enhance your learning experience.