Question

In this part, you need to answer questions on how cascading multiple filter can affect the output power.

Your answers should address:

• What is loading effect?

• Analyse an example of a band-pass filter formed by cascading a high pass and a low pass. Provide equations and discussion. This example can be different from the two designs above. Pick what is convenient for you.

• What are the techniques to minimize this Loading effect?

Answer 1

Let's start with what is loading effect.

When two networks are connected or cascaded in such a way that when network A and network B has a difference in the impedance, the circuit draws more current than usual which will lead to drop of voltage at the output. This effect is called as loading effect.

In other words, when expected voltage doesn't get delivered to load due to the mismatch of impedance then we say loading effect is occurring in an circuit.

Practically this is present in each and every circuit.

Now lets the how filter cascading effects the power gain.

This loading effect can be minimised by making the input resistance or impedance of each stage as large as possible so that the previous stage which comes in cascade doesn't significantly change the overall impedance of the circuit.

In the above circuit if you make the 2ohms value as 2Mohms then you won't see loading effect.

Also usage of buffers in between the two sections can also reduce the loading effect.

Hope this helps.

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