44.1.1. Output Resistance

Now, if we rearrange this equation what we can get is ratio of that is. So, that is the output resistance. In fact, you can further simplify this is we can say that this is. And this is you can see it is a normal approximation is. So, the output resistance it is which is quite low.

In this section, we begin with rearranging an equation to extract the output resistance of a system. The output resistance provides insights into how well a circuit can maintain its voltage when output current changes. A lower output resistance indicates better performance, meaning that the circuit can deliver a constant voltage despite variations in load. This is often crucial in amplifier design where consistent voltage is needed across various operational conditions.

Consider if you were trying to fill a bathtub with water using a hose. If the hose has a high resistance (like the output having high resistance), it would take longer to fill the bathtub and may not keep the water level steady when you open or close a faucet. In contrast, a hose with low resistance allows water to flow freely and keep the bathtub filled steadily.

Now, similar kind of analysis can be done for the common collector amplifier also to get the output resistance. So, in this case again v it is the same as ‒ v, where v is the voltage stimulus at the emitter terminal.

Here, we extend our analysis of output resistance to common collector amplifiers. In this context, we relate the voltage at the output (emitter terminal) to the voltage at the input (base terminal) with the equation v = ‒ v. This relationship helps us to determine how the output resistance behaves in this configuration. The analysis indicates that output resistance remains low similarly, which reinforces the efficiency of the common collector configuration in signal amplification.

Imagine using a water tank system where the water pressure at the outlet should match the demands at the inlet (like voltage matching). If your output is designed so that the inlet’s pressure drop is low (low resistance), the system efficiently delivers water without fluctuating pressure, similar to how a common collector keeps output stable.

Now, we like to get the expression of this current i and i it is having 3 components, one is the current flowing through this r which is the voltage here and then this current which is, so this is the second part. And then the third part it is g v and its direction it is in this direction.

In order to fully understand output resistance, we break down the total current flowing in the circuit into three components. This decomposition helps in analyzing how each part contributes to the overall behavior of the output. Each current component has a unique role in maintaining the voltage and response characteristics of the amplifier. The critical finding is that these components cooperate to ensure the model remains effective under different conditions.

Imagine a highway with three lanes. Each lane corresponds to a component of current. Just as all lanes together help to manage traffic flow smoothly, the current components collectively ensure the output remains stable and effective in the amplifier circuit, regardless of the input changes.

So, we can say that the output resistance it is low. So, we can summarize that this is low resistance.

At the conclusion of our discussion on output resistance, we conclude that both the common collector amplifier and the previous circuit examples exhibit low output resistance. This finding is significant as it means that these amplifier types can drive loads effectively without compromising their voltage stability, leading to better performance in practical applications.

Think of a sports car with a powerful engine that maintains high speed on the road with little resistance. Just like the car accelerates and maintains speed smoothly despite road conditions, a circuit with low output resistance operates efficiently, providing stable performance in various scenarios.

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