22.1.5. Summary of Voltage Amplifier Concept

What we mean by the voltage amplifier? It is an equivalent linear circuit and its main purpose is to provide the dependency of output signal on the input signal.

A voltage amplifier is a simplified version of an electronic circuit that primarily establishes how the output signal changes in response to the input signal. The core idea is to maintain a relationship between the input and output, focusing on how the input affects the output without worrying about the complexities of the entire circuit.

Imagine a water tap where the input (turning the tap) controls the output (amount of water flowing out). The voltage amplifier works in a similar way, where the input voltage controls the output voltage, just like how the amount you turn the tap determines the water flow.

The DC part is not changing, so we can probably eliminate the DC part in the simplified model to make the circuit simpler.

In designing the voltage amplifier model, we can often drop the constant DC voltage component. This simplification allows us to focus solely on how small fluctuations (the small signal variations) affect the output, making analysis much more manageable.

Think of a school where students' heights change over time but on average, their height is the same. If you want to keep track of how their heights change, you can ignore the constant average height and just measure the variations from that average.

So, we may say that the simplified model must express the relationship between this signal source or whatever the input voltage you do have to this output.

For any voltage amplifier, there are three key parameters we need to consider: the voltage gain (how much the signal is amplified), the output resistance (how much the amplifier can load the next stage), and the input resistance (which affects how much of the signal enters the amplifier). These parameters help us build an accurate model of how the amplifier will perform under different conditions.

Consider a person trying to carry groceries. The strength of the person represents the voltage gain, the size of the grocery bag symbolizes the output resistance (how much weight they can handle), and the opening of the bag signifies the input resistance (how many groceries can initially enter). Together, they define how effectively groceries can be brought home.

Now, how do we capture the loading effect? We can put a resistance here ... to take care of the loading effect at the output port.

When connecting other devices to an amplifier's output, the additional load can alter the amplifier's performance. To account for this, we introduce an output resistance in our model, allowing us to predict how the output voltage might be affected by varying loads.

Similar to how adding more passengers in a car can affect its speed, connecting a load to a voltage amplifier changes how the amplifier performs, and this is captured by the output resistance in our model.

So the simplified model as I said, focuses on the input to output signal relationship primarily.

The key objective of the voltage amplifier model is to accurately describe the relationship between the input signal and the resulting output signal. This ensures that we can predict how variations in the input will affect the output, which is crucial for designing and analyzing electronic systems.

Think of a dial thermostat that adjusts the temperature based on the current room temperature. The relationship between the room temperature (input) and the heating or cooling provided by the thermostat (output) mirrors how a voltage amplifier changes input signals to produce modified output signals.

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