# Second order low pass filter with unity gain

• Henry
In summary, the conversation discusses the design of a second order filter with unity gain for a piece of coursework. The method proposed by one person is deemed a suitable candidate, but not ideal. The application and design constraints are also mentioned, and the use of an active filter is suggested for a flatter response. It is ultimately determined that the proposed design is sufficient for the given task.
Henry

## Homework Statement

I need to design a second order filter with unity gain.

## Homework Equations

None - not taking component values into account for now.

## The Attempt at a Solution

Is this a correct method of creating a 2nd order low pass filter with unity gain?

That is one such candidate; not what I'd consider a good representative of such a filter, but it certainly fits.

What is the application you need it for?

I had to design a two part system with a transimpedance amplifier then a second order low pass filter for a piece of coursework. It's specified that we cannot use a power supply larger than 5v for the opamps though, so I designed the system to take care of all of the gain during the transimpedance stage.

Sorry if that sounds confusing, I'm still getting my head around this a little bit.

What you have there is basically a passive two-stage filter, so its Bode plot is not nice and level over any range, it begins drooping right from DC.

How would I go about changing that?

Henry said:
How would I go about changing that?
Do you need it to be any different, though?

For flatter responses, google: active filters.

Probably not, the question wasn't particulary specific, it just asked for a second order low pass filter so that's probably fine. Thank you for your help!

## What is a second order low pass filter with unity gain?

A second order low pass filter with unity gain is an electronic circuit that is used to filter out high frequency signals from a given input signal. It is called a "low pass" filter because it allows low frequency signals to pass through while attenuating or reducing the amplitude of high frequency signals. The term "unity gain" means that the output signal has the same amplitude as the input signal.

## How does a second order low pass filter with unity gain work?

A second order low pass filter with unity gain works by using a combination of resistors, capacitors, and op-amps to create a frequency-dependent voltage divider. This means that at low frequencies, the output voltage will be almost equal to the input voltage, while at high frequencies, the output voltage will be significantly lower than the input voltage. This is due to the fact that the capacitors in the circuit act as a high pass filter, allowing low frequencies to pass through while blocking high frequencies.

## What are the advantages of using a second order low pass filter with unity gain?

One advantage of using a second order low pass filter with unity gain is that it is a simple and cost-effective way to filter out high frequency noise from a signal. It also has a steeper roll-off (decrease in amplitude) compared to first order filters, meaning that it is better at attenuating high frequency signals. Additionally, it has a flat frequency response in the passband, which means that it does not introduce any distortion to the filtered signal.

## What are the applications of a second order low pass filter with unity gain?

Second order low pass filters with unity gain are commonly used in audio and music equipment to remove unwanted high frequency noise from the signal. They are also used in communication systems to filter out interference from other signals. In addition, they can be found in power supplies to filter out high frequency noise from the mains supply, and in electronic circuits to protect sensitive components from high frequency signals.

## What are the differences between a first order and second order low pass filter with unity gain?

The main difference between a first order and second order low pass filter with unity gain is the roll-off. A second order filter has a steeper roll-off, meaning that it can attenuate high frequency signals more effectively. Additionally, a second order filter has a flatter frequency response in the passband, and can achieve a lower cutoff frequency compared to a first order filter. However, a second order filter is more complex and requires more components, making it more expensive to build.

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