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.
Current Mirror Basics
Unlock Audio Lesson
Signup and Enroll to the course for listening the Audio Lesson
Today weβre going to start with current mirrors. Can anyone tell me what a current mirror is?
Isn't it a circuit that replicates a current from one branch to another?
Exactly, Student_1! A current mirror allows us to control current in different parts of a circuit, ensuring uniformity. Think of it like a 'copy machine' for current. One of the key benefits of using a current mirror in analog design is the replication of stable reference currents.
What applications do these current mirrors have?
Great question! Current mirrors are often used in amplifiers, such as common emitter configurations, and in differential amplifiers. Remember, amplifiers need precise biasing for optimal operation.
So they help in getting consistent current outputs?
Yes, exactly, Student_3! This ensures that the transistors stay in the active region based on the mirrored current. Let's move on to how we represent these using small signal models.
To sum up, current mirrors play a crucial role in maintaining stable current levels and biasing in circuit designs, particularly in amplifiers.
Small Signal Modeling
Unlock Audio Lesson
Signup and Enroll to the course for listening the Audio Lesson
Now, letβs dive into small signal modeling of current mirrors. Why do we need small signal models?
I guess it's to analyze how the circuit behaves with AC signals?
"Exactly right, Student_4! Small signal models help us analyze the gain and frequency response. For instance, we make an open circuit approximation for DC conditions.
Applications in Amplifiers
Unlock Audio Lesson
Signup and Enroll to the course for listening the Audio Lesson
Letβs see how current mirrors are applied in amplifiers today. Weβll start with the common emitter amplifier.
How do current mirrors work in this application?
Excellent question! In a common emitter configuration, a current mirror acts as the load, providing a constant current while maximizing voltage gain. It stabilizes the collector current, thus improving the amplifier's performance.
And it does this while ensuring both transistors are in the active region?
Precisely! Letβs say we have two identical transistors working as a mirror; their characteristics ensure that the currents are nearly equal, hence making signal amplification more robust.
Can this technique be used for MOSFET amplifiers as well?
Yes, the same principles apply. Current mirrors enhance gain and maintain the linearity of the amplifier circuit, regardless of whether we use BJT or MOSFET.
In summary, the current mirror enhances amplifier performance by replicating currents effectively, ensuring the active operation of transistors.
Introduction & Overview
Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.
Quick Overview
Standard
The section explains the functioning of current mirrors in various configurations like common emitter, common source amplifiers, differential amplifiers, and their small signal models. It details both BJT and MOSFET implementations and their practical applications in analog electronic circuits.
Detailed
Illustrative Circuit Examples
This section discusses the applications of current mirror circuits in various analog electronic configurations. Understanding current mirrors is fundamental for designing amplifiers, particularly in the use of BJT and MOSFET devices. The current mirror serves primarily to mirror or replicate a reference current within different sections of a circuit.
Key Topics Covered:
- Current Mirror Basics: Current mirrors are used to replicate currents to maintain uniformity in various amplifier configurations.
- Amplifier Configurations: The applications are showcased in configurations such as common emitter, common source, common collector, and differential amplifiers.
- Small Signal Modeling: The detailed approach includes creating small signal models for both BJT and MOSFET current mirrors in DC and AC conditions. The models help in analyzing the performance of amplifiers with respect to their gain and response.
- Examples in Analog Design: The lectures provide examples of how current mirrors can be implemented in practical circuits, discussing the effects of transistor characteristics on performance.
- Applications in Differential Amplifiers: A specific focus is placed on how current mirrors function not only as biasing elements but also as integral parts of the signal path in differential amplifiers.
Through understanding these concepts, students gain a thorough insight into the importance and utility of current mirrors, essential for anyone working in analog electronics.
Youtube Videos
Audio Book
Dive deep into the subject with an immersive audiobook experience.
Current Mirror Usage in Amplifiers
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
So, according to our overall plan we are in week-9. In fact, this is course module-8. We have talked about current mirror, its operating principle and analysis in the previous lecture. Today we are going to discuss more detail of the current mirror specifically its application and we do have different applications for this current mirror. One is in common emitter and common source amplifier based on whether it is BJT or MOSFET based implementation. Likewise, in common collector and common drain and common base and common gate and also in differential amplifier.
Detailed Explanation
In this chunk, the focus is on the applications of current mirrors in different amplifier configurations. The current mirror can be utilized in common emitter amplifiers (BJT) and common source amplifiers (MOSFET), as well as in other configurations such as common collector and differential amplifiers. Each application leverages the current mirrorβs ability to provide a stable reference current, which is crucial for properly biasing the amplifier stages.
Examples & Analogies
Think of a current mirror like a manager in a company who ensures that a certain number of employees are always available to work on important tasks. Just as the manager keeps the workforce stable and reliable, the current mirror maintains a consistent current flow through the amplifier, allowing it to perform its job effectively.
Small Signal Model for Current Mirrors
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
We need to understand the small signal model of current mirror and to go into the small signal model we do have two possible situations. One is the current mirror may not be carrying any signal namely under DC condition what is the small signal equivalent circuit and then we do have the second possible situation where the current mirror may carry signal in the form of current. And we will be talking about both BJT and MOSFET version of the small signal model.
Detailed Explanation
This chunk discusses the different conditions under which a current mirror operatesβnamely, under DC conditions without any signals and under AC conditions when it carries signal currents. When operating under DC conditions, the small signal equivalent is straightforward since the circuit behaves as if it is open, while in the AC case, the circuit must account for varying input signal currents. Understanding these models is crucial for analyzing how the current mirror responds in different operational contexts.
Examples & Analogies
Imagine you're adjusting the volume on a speaker. When thereβs no music (DC condition), the speaker is completely silent. However, when you play music (AC condition), the speaker responds by vibrating in different ways. Similarly, in electronics, when thereβs no signal, the current mirror remains static, but it must dynamically adjust when an input signal is present.
Small Signal Model with Signal Current
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
Now, in this situation, we have the basic current mirror and now the difference here it is along with the DC reference current it is also having signal current. So, this signal current it is again it is coming from either DC you are whatever it is, but finally, at the collect the drain node of the MOSFET it is arriving and it may be producing a voltage here.
Detailed Explanation
This chunk elaborates on a scenario where the current mirror has a static DC reference current and simultaneously receives an additional AC signal current. In this case, the voltage at the output (drain node) is affected by both the reference current and the signal input. This is crucial for applications that require the mirror to amplify the input signal while maintaining the reference current's accuracy and stability.
Examples & Analogies
Consider a swimming pool where the water level is maintained at a certain height (the DC current) while simultaneously adding buckets of water to create waves (the AC signal). The overall water level will be influenced by both the constant supply of water and the waves created by the added buckets, just like the output voltage of the current mirror is affected by both the DC and AC currents.
Implementation in Common Emitter and Common Source Amplifiers
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
To start with let me consider common emitter or common source amplifier let me see which one I do have yeah and to start with I do have common emitter amplifier with active load. So, this is this is the main circuit where transistor-1 it is working as amplifying device, input signal we are feeding through the coupling capacitor and then R it is providing bias current I .
Detailed Explanation
In this section, examples of using current mirrors within common emitter and common source amplifier configurations are presented. The current mirror can act as an active load, enhancing the performance of these amplifiers. By stabilizing the bias current and ensuring that the amplifying transistor operates efficiently, the current mirror significantly improves gain and linearity in the circuit.
Examples & Analogies
Think of a common emitter amplifier as a person giving a speech. The current mirror acts like a microphone, amplifying the speaker's voice (input signal) while ensuring the right amount of sound (current) is projected for clarity. Just as the microphone ensures a steady volume level, the current mirror helps maintain consistent performance for the amplifier, allowing for a clearer output.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
-
Current Mirror: A circuit design used to replicate current between branches.
-
Small Signal Model: A technique used for the analysis of circuit behavior under small signal variations.
-
Common Emitter Amplifier: A type of amplifier that uses a BJT for voltage amplification.
-
Common Source Amplifier: A type of amplifier configuration that uses a MOSFET.
-
Transconductance: The parameter indicating how effectively a transistor converts voltage into current.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
-
The common emitter amplifier setup uses a current mirror to stabilize the collector current.
-
In a differential amplifier, a current mirror maintains consistent biasing across the input transistors.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
π΅ Rhymes Time
-
To mirror the current in a stream, keeps it stable, like a dream.
π Fascinating Stories
-
Imagine two identical twins sharing the same ice cream. Whatever amount one has, the other reflects it perfectly. This is how current mirrors work; they ensure currents are equal.
π§ Other Memory Gems
-
For amplifiers, remember: 'Current Mirrors Amplify Consistency' - CMAC.
π― Super Acronyms
CMA
- Current Mirror Applications.
Flash Cards
Review key concepts with flashcards.
Glossary of Terms
Review the Definitions for terms.
-
Term: Current Mirror
Definition:
A circuit configuration that replicates a reference current in order to achieve consistency and stability across multiple branches of a circuit.
-
Term: Small Signal Model
Definition:
An analytical technique used to analyze the behavior of circuits when small perturbations are introduced in voltage or current.
-
Term: Common Emitter Amplifier
Definition:
An amplifier configuration using a BJT that provides voltage amplification with an inverted output phase.
-
Term: Common Source Amplifier
Definition:
An amplifier configuration using a MOSFET that provides voltage amplification, analogous to a common emitter configuration.
-
Term: Transconductance (g_m)
Definition:
The rate of change of the output current with respect to the input voltage in a transistor.