38.1.7. Frequency Response Discussion

The overall plan; as I said that in the previous week we have discussed about the frequency response of CE amplifier for which we have detailed discussion about R-C and C-R circuit and then you know we have discussed about the common source amplifier particularly with circuit analysis. Numerical portion it was not covered, so today we are going to discuss numerical examples of common source amplifier.

In this introduction, we are recapping what was discussed in the previous class regarding the frequency response of common emitter (CE) amplifiers and common source amplifiers. The CE amplifier has both R-C (Resistor-Capacitor) and C-R (Capacitor-Resistor) circuits, which affect its frequency response, hence the earlier detailed discussions. Today, we aim to explore the numerical aspects of these amplifiers, particularly focusing on how to analyze them mathematically.

Think of an amplifier as a speaker system for your home. Just as the quality of sound you hear can be influenced by the type of speakers and how they are set up (including any additional equalizers or filters), the frequency response of an amplifier is influenced by the resistance and capacitance in the circuit. If set well, you'll achieve the best sound (or amplification) possible.

In the previous week what we have discussed? It is in case if we have say common in any amplifier which is having say preceded C-R circuit and then followed by the R-C circuit, then the corresponding model of the circuit, it is given here.

This part serves as a brief recap of the last lecture. We revisited how amplifiers consist of interconnected C-R and R-C circuits, leading to the overall behavior of the amplifier. Understanding how these parts interact is key to analyzing an amplifier's frequency response.

Imagine making a smoothie. The ingredients (like fruits and yogurt) need to be mixed together in the right proportions (similar to electrical components in a circuit) for the best taste (output response). If you do not add enough of one ingredient (e.g., resistance), the smoothie might be too thick and not smooth (the frequency response is not optimal).

Let us; so, that is what we have discussed in the previous day, now we are going to discuss about CE amplifier having self-biased arrangement.

We are now shifting our focus to a specific type of CE amplifier — the self-biased arrangement. This configuration is important because it allows the amplifier to operate consistently over wider ranges of input signals and maintains bias without external voltage sources. This section will break down the mechanics of this setup.

Think of a self-biased amplifier like a self-regulating garden. Instead of needing constant water (external bias) to maintain the plants, a self-sustaining garden uses rainwater and soil to keep plants thriving at optimal conditions, similar to how self-bias maintains the amplifier's operation.

Yes; so, this is the core part of the circuit and as I said that the signal we are directly feeding here at the input and the output we are observing at this point.

This section analyzes the core of the self-biased CE amplifier. Here, the input signal affects the output directly, and we need to understand how these interactions create gain. The concepts of input and output voltage connections are critical at this stage, as these relationships define the amplifier's behavior.

This is like someone telling you a joke (input) that makes everyone laugh (output). The strength of the joke (signal gain) depends directly on how well it is delivered. Similarly, the gain in an amplifier depends on the input voltage and the reactions of the components within.

So, to summarize, so what we are obtaining here it is this circuit, this circuit is having voltage gain of a and then input resistance it is R ⫽ R and then r + R (1 + β).

In this segment, we explore how to calculate the voltage gain and input resistance of the self-biased CE amplifier. The voltage gain is a measure of how much the output signal increases compared to the input signal. We also express the input resistance in terms of the circuit components, highlighting the complexities introduced by the self-bias configuration.

Imagine a speaker that can either amplify or muffle sound based on how closely you are standing to it. The closer you are (lower input resistance), the better you can hear (higher gain) the music. Similarly, in an amplifier, the right balance between input resistance and gain can significantly influence the output quality.

So, what we said here it is this should be R and in addition to that R = R . So, this information, these three expressions basically the information about the core CE amplifier, we are going to use to get the frequency response of this entire circuit.

Finally, we discuss how the gained information about the voltage gain and input resistance will enable us to derive the overall frequency response for the whole circuit. We will combine the frequency responses of the individual components (C-R and R-C sections) to understand how they work together in amplifying a signal and influencing bandwidth.

Imagine piecing together a jigsaw puzzle. Each piece represents a part of the amplifier's circuit, and when they come together, they create a clear picture (overall frequency response). The better the pieces fit together, the clearer the final image will be, which is analogous to achieving optimal performance from the amplifier.

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