46.4. Output Resistance Discussion

So, if you see the output resistance. So, we do have the same small signal model and to know the output resistance, we have to make the signal = 0 namely base terminal we are making it AC ground. We are stimulating the circuit with v and we are observing the corresponding current flowing through the circuit. So, what we have here it is this i, it is summation of all these currents.

To determine the output resistance of the common collector amplifier, we need to set the input signal to zero. This means we treat the input as AC ground, which simplifies the analysis. By applying a voltage to the circuit and observing the current, we can sum the currents in the circuit to find the output resistance. Essentially, we're looking at how much the current can change in response to a voltage at the output.

Imagine a water tank connected to several pipes. When we apply a force to put water into the tank (input voltage), we can observe how much water flows out through the tank's outlet (output current). By keeping track of the water flow, we can understand the resistance of the pipes to that flow.

The current flowing through the device here whatever voltage dependent current source, it is g v and incidentally v = ‒ v. So, we can say that this current is g v and then, we also have the current flowing through this device and that device, it is we do have say v, ‒ whatever the current flow we do have.

In this part, we analyze the relationships between various currents in the circuit. The current through the voltage-dependent source is largely determined by the output voltage, and this affects how the output current behaves. By recognizing how these currents interrelate, we can better understand the overall behavior of the circuit and determine its output resistance.

Think of a traffic system where cars (currents) are flowing through different routes (devices). The amount of traffic on one route can influence the traffic flow on another. If one road sees an increase in cars, it can cause delays or changes in the traffic on nearby roads, similar to how currents affect each other in an electronic circuit.

Now, for simplicity what we have done is that since we are stimulating this terminal by v directly, instead of considering this entire circuit and try to find what will be the impedance. We may split this part; one is this part and then, rest of the things.

To simplify the calculation of output resistance, we can break down the circuit into simpler parts. By isolating the current from the various elements, we can calculate the output resistance through these sections rather than dealing with the entire circuit at once. This approach makes the analysis more manageable and allows us to get a clearer result in terms of output resistance.

Consider preparing a dish in your kitchen. Instead of trying to gauge the taste of the final dish with all ingredients at once, you might taste each ingredient separately. This way, you can adjust the seasoning or flavors accordingly, making it easier to achieve the desired taste.

So, the total output resistance it is the resistance coming from this encircle part and then, r part. So, this is again you may consider this is very high. So, we can say that you can neglect this part and you can consider only this one.

In this step, we focus on simplifying our findings by discarding elements that do not significantly impact the overall output resistance. If some resistive components in the circuit exhibit very high values, we can ignore them in our calculations, leading to a simpler computation of the output resistance.

Think about carrying multiple bags while shopping. If you realize one bag is empty or weighs almost nothing, you can ignore its impact on how heavy your load feels. By disregarding the negligible weight, you're left with a clearer understanding of how hard it is to carry everything.

So, the conclusion is that this output resistance in the order of which is quote and unquote load ok.

The ultimate conclusion regarding output resistance indicates how the circuit's performance behaves under load. The output resistance should be low to allow for better power transfer and efficiency in the circuit operation. Low output resistance is a desirable feature in many amplifier designs.

Imagine a garden hose used for watering plants. If the hose has a wide diameter, it allows water to flow easily and reach the plants efficiently without much resistance. If it were narrow (high resistance), it would struggle to deliver enough water, wasting time and effort.

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