93.1.3. Non-ideal Situations and Source Resistance

So, let us consider non ideal situations to start with let we consider that we do have a source resistance called R_s.

In this chunk, we introduce the concept of non-ideal conditions that can affect the performance of electronic circuits. Specifically, we mention that there exists a source resistance (R_s), which could affect the output resistance of the circuit in various configurations. This is important because ideal scenarios assume no resistance, but real components will have some resistance that can alter circuit behavior.

Think of it like a water pipe—if the pipe is perfectly smooth, water flows freely (ideal situation). But if there are bumps or leaks (source resistance), the water flow will be reduced (non-ideal situation).

In this condition; v_in, the input voltage at this port can be written in terms of βv_x. In fact, it is ‒ βv, and then the voltage appearing here is a part of this voltage.

This chunk explains how the input voltage (v_in) changes when a source resistance is present. The input voltage becomes a function of the feedback factor (β) and another voltage (v_x). This dependence shows that the presence of source resistance alters how we calculate input voltage in the circuit, which will ultimately influence the output.

Imagine a car engine that needs fuel (voltage). If there's a filter (source resistance), less fuel reaches the engine, affecting its performance. The same goes for the voltage—less ideal conditions lead to lower input voltage.

So, we can say that i = ‒ β′v, where β′ = β × R_y / (R_s + R_y).

In this chunk, we relate the current (i) flowing through the circuit to the input voltage and the feedback factor after considering the source resistance. The relationship shows that the feedback factor β can also change due to the presence of resistances in the circuit, implying that output current is now dependent on both the input conditions and the resistances involved.

Picture a crowded event where a limited number of entry points (electrical resistances) affects how quickly people (current) can enter. More entry points allow for smoother flow, while fewer make it harder. The current flow changes based on these resistances.

So, we need to put plus R_out_β and the corresponding β we can call it is β′′.

This chunk wraps up the discussion by indicating the adjustments made to account for output resistance in the feedback circuit. It notes that as resistance factors are introduced one by one, the cumulative effects are considered, allowing us to derive a new feedback parameter (β′′) that reflects these changes.

Think of adjusting the pressure of water flowing through various pipes that lead into a sink. The more pipes you have (series resistance), the more you need to account for pressure loss based on how many exits there are (β). Each change in resistance alters the flow.

So, if I consider all the three non-ideal factors, then I will be getting the R_out = R_in_β + R_out_β.

This final chunk summarizes the overall impact of combining multiple non-ideal factors. It emphasizes that output resistance will depend on a sum of contributions from different parts of the circuit, showing how real-world scenarios complicate the ideal conditions that might have initially been assumed.

Just like cooking—a recipe may work perfectly in isolation, but multiple ingredients (like spices, heat levels, and timing) influence the final dish. Similarly, in electronic circuits, various resistances impact performance, leading to a final output that may differ from the expectations set by ideal conditions.

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