Professional Courses
Industry-relevant training in Business, Technology, and Design to help professionals and graduates upskill for real-world careers.
Categories
Interactive Games
Fun, engaging games to boost memory, math fluency, typing speed, and English skillsβperfect for learners of all ages.
Typing
Memory
Math
English Adventures
Knowledge
Interactive Audio Lesson
Listen to a student-teacher conversation explaining the topic in a relatable way.
Introduction to Current Mirrors
Unlock Audio Lesson
Signup and Enroll to the course for listening the Audio Lesson
Good afternoon, class! Let's start by discussing what a current mirror is. Essentially, it's a configuration that allows one transistor to replicate the current flowing through another transistor. Can anyone tell me why this might be useful in an amplifier?
It helps to control the current more precisely in amplifiers, right?
Exactly! By using a current mirror, we can set a reference current, ensuring stable operation. Can anyone give me an example of where we might see current mirrors in action?
Common collector amplifiers, as well as common drain ones, right?
That's correct! Current mirrors are crucial in both configurations. Remember the acronym 'CAR'βCommon Amplifier Referencesβto help retain this concept. Letβs move on to how they operate in these amplifiers.
Operation in Common Collector Amplifiers
Unlock Audio Lesson
Signup and Enroll to the course for listening the Audio Lesson
When we use a current mirror in a common collector amplifier, the key is that the reference current affects the overall collector current. Can anyone recap what this means for the gain of the amplifier?
It determines the gain by influencing the output current based on the input current, right?
Spot on! The gain can actually be derived from the small-signal model. What do you think would happen to gain if we increased the reference current?
I think the gain would increase because more current would flow through the output, right?
Correct! Higher reference current increases the output current, which directly affects gain. Remember: 'More Current, More Gain'βthatβs a good mnemonic! Let's look at how this concept translates to MOSFET common drain amplifiers next.
Common Drain Amplifiers
Unlock Audio Lesson
Signup and Enroll to the course for listening the Audio Lesson
In common drain amplifiers using MOSFETs, we also utilize current mirrors. The concepts are similar to BJTs, but defined in voltage instead of current. What expressions can we derive for these setups?
We can derive the current flowing through the MOSFETs based on the supplied bias and the load.
Absolutely! The relationship needs to factor in both bias currents and the resistance present. How might this change if we ensure that all devices are identical?
If they are all identical, we can calculate the total current more effectively since their parameters will match.
Great observation! Matching devices ensure performance consistency. Always remember: 'Identical Devices, Predictable Performance.' Letβs summarize what we learned.
Current Mirrors in Differential Amplifiers
Unlock Audio Lesson
Signup and Enroll to the course for listening the Audio Lesson
Moving on to differential amplifiers, current mirrors replace tail resistors. Why is that beneficial?
It improves the common mode gain, right?
Exactly! It allows for better matching and stability in the output signals. What is the relationship between common mode gain and differential gain?
Lowering common mode gain improves the differential response, making the amplifier more effective for intended signals.
Perfectly put! To solidify this, keep in mind the phrase: 'Lower Noise, Higher Signals.' That sums up our exploration of current mirrors in amplifiers.
Conclusion and Applications
Unlock Audio Lesson
Signup and Enroll to the course for listening the Audio Lesson
As we wrap up, current mirrors have diverse applications and improve amplifier performance significantly. Can someone summarize the key points we've covered?
They provide precise current control, improve gain, and help reduce common mode gain in amplifiers!
Excellent! Remember these concepts: they are crucial for modern analog designs. Think of current mirrors as the backbone of amplifier stability. What session are we tackling next?
Differential amplifier applications!
That's right! Let's delve into those exciting frontiers next class. Great job today, everyone!
Introduction & Overview
Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.
Quick Overview
Standard
This section explores the concept and utility of active load current mirrors, particularly in common collector and drain amplifier circuits. It explains how current mirrors improve gain and reduce common mode gain in differential amplifiers.
Detailed
Active Load Current Mirror
In this section, we delve into the function and applications of active load current mirrors within common collector and common drain amplifiers. The current mirror is constructed using transistors which allow for precise current control based on reference currents.
Key Concepts
- Current Mirror Construction: A current mirror typically consists of multiple transistors where the collector current of one transistor mirrors the current flowing through another, set by a reference current.
- Common Collector Amplifier: The section details how current mirrors function as active loads and their influence on gain. The gain for a common collector amplifier utilizing a current mirror is derived from the small signal equivalent circuit, emphasizing the role of transistor resistance.
- Common Drain Amplifier: Similar principles apply when using MOSFETs in a common drain configuration. Here, the detailed relationships between bias currents and their impacts on circuit performance are explored.
- Differential Amplifier Improvements: The current mirror is shown to replace passive loads and tail resistors in differential amplifiers, improving both differential mode gain and decreasing common mode gain. The performance enhancements are quantified via approximations of current through mirrored components.
Overall, understanding how active current mirrors operate and interact within amplifier circuits provides essential insight into analog circuit design.
Youtube Videos
Audio Book
Dive deep into the subject with an immersive audiobook experience.
Introduction to Current Mirrors in Amplifiers
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
So, dear students welcome back after the break. So, before the break we were talking about the usage of current mirror for CE amplifier, and also CS amplifier. Now we also can see that usage of current mirror for Common Collector amplifier as well. So, here we do have the transistor level circuit transistor-1 it is the main amplifying transistor input port is here.
Detailed Explanation
This chunk introduces the concept of current mirrors being used in different types of amplifiers, specifically mentioning CE (Common Emitter), CS (Common Source), and Common Collector configurations. It sets the stage for discussing how a current mirror can enhance the performance of these amplifiers by providing a controlled reference current. Understanding different amplifier types is crucial as they each have unique applications in electronic circuits.
Examples & Analogies
Think of a current mirror like a water faucet. If you want a specific amount of water (current) flowing to a plant (amplifier), you set the faucet to allow that much water. Similarly, a current mirror helps set the flow of electrical current to maintain consistent performance in electronic devices, making them operate smoothly.
Reference Current Setup
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
And then the output port it is here and earlier what we said is that the current of this transistor it can be set by one reference current. So, instead of having reference current this is what we do have the implementation of the current source. In fact, if you see that it consists of a bias resistor R maybe you can see bias.
Detailed Explanation
This chunk discusses the importance of setting a reference current for the operation of the amplifier. In electronic circuits, the reference current is crucial for determining how much current flows through the main amplifying transistor, allowing for consistent behavior. The current source is associated with a bias resistor, which helps in generating this reference current, ensuring stability in the amplifier's performance.
Examples & Analogies
Imagine a railway system where the train (current) runs on a track (circuit). The speed of the train needs to be regulated to ensure safe travel. The reference current sets a limit on how fast the train can go, much like the bias resistor ensures the amplifier operates at the optimal current level.
Current Mirror Construction
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
We can say that the collector current of transistor-2 I it is well approximated by Γ I . So, this is the exact equation assuming transistor-2 and transistor-3 they are identical and then this may be well approximated by Γ I.
Detailed Explanation
Here, the construction of the current mirror is discussed, particularly focusing on transistors-2 and-3, which are ideally identical. The relationship between the collector current of transistor-2 and the reference current in transistor-3 is mathematically established. This principle is vital for ensuring that the current mirror can accurately reflect the currents and maintain the same characteristics for both transistors.
Examples & Analogies
Consider two identical twins: one has a specific talent (current) and we expect the other to have the same talent. Similarly, in a current mirror, when one transistor (twin) has a certain amount of current flowing, we rely on the other identical transistor to mirror that exact behavior.
Analyzing Output through Small Signal Equivalent Circuit
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
Once we get the DC operating point then to find the gain from input to primary output we can draw the small signal equivalent circuit and since the current mirror here it is not carrying any signal. So, the equivalent circuit small signal equivalent circuit coming out of the current mirror it is only r of transistor-2.
Detailed Explanation
This section explains how to find the voltage gain of the amplifier using its small signal equivalent circuit once the DC operating point is established. It highlights that because the current mirror doesn't carry audio or varying signals, the equivalent circuit simplifies significantly. This step is essential for calculating the performance metrics of the amplifier, particularly the gain.
Examples & Analogies
Imagine a librarian processing books reading them (analog signals) to determine their importance (gain). However, if a section is strictly for storage (the current mirror), the librarian only needs to note down where the books are, simplifying the organization of the information without altering it.
Application in Common Drain Amplifier
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
So, similar to common collector amplifier the current mirror can also be used for common drain amplifier which is the MOSFET counterpart of this circuit.
Detailed Explanation
This chunk addresses the application of current mirrors in different types of amplifiers, specifically mentioning the Common Drain amplifier (analogous to Common Collector but using MOSFET technology). This emphasizes the versatility of current mirrors in both bipolar and MOSFET circuits, showcasing their essential role in analog design.
Examples & Analogies
Think of a universal adapter for different devices. Just as a universal adapter can facilitate charging for various types of electronics regardless of brand or model, a current mirror serves multiple amplifier configurations in electronics, ensuring they function optimally.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
-
Current Mirror Construction: A current mirror typically consists of multiple transistors where the collector current of one transistor mirrors the current flowing through another, set by a reference current.
-
Common Collector Amplifier: The section details how current mirrors function as active loads and their influence on gain. The gain for a common collector amplifier utilizing a current mirror is derived from the small signal equivalent circuit, emphasizing the role of transistor resistance.
-
Common Drain Amplifier: Similar principles apply when using MOSFETs in a common drain configuration. Here, the detailed relationships between bias currents and their impacts on circuit performance are explored.
-
Differential Amplifier Improvements: The current mirror is shown to replace passive loads and tail resistors in differential amplifiers, improving both differential mode gain and decreasing common mode gain. The performance enhancements are quantified via approximations of current through mirrored components.
-
Overall, understanding how active current mirrors operate and interact within amplifier circuits provides essential insight into analog circuit design.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
-
Using a current mirror in a common collector amplifier allows for stable operation and consistent gain by controlling the reference current.
-
In a common drain amplifier, a current mirror helps maintain consistent output characteristics, benefiting the conversion of varying input signals.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
π΅ Rhymes Time
-
In amplifiers we find our base, Current mirrors put us in the race.
π Fascinating Stories
-
Imagine a school where each student mirrors their top achiever. This is akin to how current mirrors help amplifiers shine brighter.
π§ Other Memory Gems
-
C for Common, M for Mirror, R for ReflectionβTogether they amplify!
π― Super Acronyms
CAM
- Current
- Amplifiers
- MirrorsβA reminder of their interconnected roles.
Flash Cards
Review key concepts with flashcards.
Glossary of Terms
Review the Definitions for terms.
-
Term: Current Mirror
Definition:
A circuit that sets the current flowing through one or more transistors to match a reference current.
-
Term: Common Collector Amplifier
Definition:
An amplifier configuration where the output voltage is taken from the emitter terminal.
-
Term: Common Drain Amplifier
Definition:
A MOSFET amplifier configuration that serves a similar purpose to a common collector, where the output is taken from the source.
-
Term: Differential Amplifier
Definition:
An amplifier that amplifies the difference between two input voltages.
-
Term: Reference Current
Definition:
A stable current value that sets the operating point in a current mirror configuration.