85.2.6. Closing Remarks and Future Topics

Let me summarize the presentation in these 3 parts of this lecture what we have done it is we have started with a small signal small signal model of current mirror particularly, under DC condition as well as whenever it is carrying the signal current for both BJT and MOSFET versions.

In this lecture summary, the instructor highlights the key areas covered. The session began with an exploration of the small signal model of a current mirror, looking specifically at its behavior under direct current (DC) conditions and while it was transmitting signal currents. This means they discussed how current mirrors work to maintain a consistent current in different conditions using both BJT (Bipolar Junction Transistor) and MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) components. This understanding is crucial for students, as current mirrors are a fundamental building block in electronic circuits.

You can think of a current mirror as a water faucet that maintains a consistent flow of water regardless of how many pipes are branching off. If you increase or decrease the flow in one pipe, the faucet automatically adjusts to keep the flow stable and equal in other branches. This makes current mirrors essential for stabilizing current levels in electronic devices.

After that we have talked about usage of current mirror particularly as bias elements for common emitter amplifier and common source amplifier particularly for the load part and we have seen that it enhances the gain of both the amplifiers.

The discussion then shifted to the applications of current mirrors in amplifiers. Current mirrors are used as biasing elements in common emitter and common source amplifiers, providing a stable current necessary for reliable operation. The text indicates that their use in these configurations helps to enhance the overall gain of the amplifiers, meaning they can amplify signals more effectively. Gain refers to how much an amplifier boosts the input signal.

Imagine you have a microphone connected to a speaker. If the microphone doesn't get steady power, the sound might be inconsistent and hard to hear. But when you have a reliable power source (like a current mirror providing consistent current), the speaker can produce clear and amplified sound. Similarly, in amplifiers, a steady current means clear amplified signals.

Also, we have discussed about the usage of current mirror as a biasing element for common collector and common drain amplifier.

In addition to common emitter and common source configurations, the lecture also covered how current mirrors serve as biasing elements in common collector and common drain amplifiers as well. These amplifiers require consistent biasing to function properly, and the use of current mirrors helps ensure this consistency. This contributes to the amplifiers’ effective operation and improves their performance.

Think of a bicycle that needs the right tire pressure to run smoothly. If the pressure is too low or too high, the ride will be uncomfortable. Similarly, biasing an amplifier with a current mirror ensures that it runs smoothly, providing consistent performance whether it's a common collector or common drain type.

Finally, we have talked about usage of current mirror in differential amplifier. And it is having two kinds of application, one is for biasing element and we have seen that it improves the common mode gain and differential mode gain.

The presentation concluded with a focus on the use of current mirrors in differential amplifiers. These amplifiers are unique because they amplify the difference between two input signals, making them essential in many signal processing applications. Current mirrors improve both the common mode gain, which refers to how well the circuit can reject noise common to both input signals, and the differential mode gain, which deals with amplifying the actual difference. This enhancement is crucial for applications where signal integrity is paramount.

Imagine a scale that measures weight. If a bag on one side is heavy and a light bag on the other, you want the scale to show the difference accurately without being affected by the weight of its base. Current mirrors in differential amplifiers serve a similar purpose—they enhance the ability to differentiate between two signals while ignoring surrounding noise.

In addition to that finally, we have talked about the usage of the current mirror as active mirror load. This helps to convert the output port in the form of single ended and in addition it also decrease the common mode gain.

The lecture also discussed the role of current mirrors as active loads. Essentially, using current mirrors as loads can help convert differential outputs into single-ended outputs, which is often more useful in practical applications. Moreover, this configuration significantly reduces the common mode gain, enhancing performance by minimizing unwanted noise and interference in the signal output.

Consider a nightlight that only shines a soft, steady light without any flickering or fluctuating brightness. When you use an active current mirror load in an amplifier, you create a similar effect: it provides steady output while filtering out unnecessary variations (common mode noise). This is how it helps improve the clarity of signals in real-world devices.

I think that is all to cover. In the next class we will be talking about numerical examples.

The instructor concludes the session by summarizing the topics covered and indicating that the next class will delve into numerical examples. This is likely intended to solidify understanding by applying the theoretical concepts learned to practical numerical problems, helping students gain hands-on experience with the material.

Think of cooking: after reading a recipe and preparing a dish, the next step is to taste it to see how well it turned out. Similarly, by working on numerical examples in the next class, students will get to 'taste' the concepts they've learned about current mirrors and amplifiers, solidifying their understanding through practice.

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