# [Homework] Identify Filter type

• bran_1
In summary, the circuit is a band reject filter that passes lower frequencies but blocks the higher range.
bran_1

## Homework Statement

Identify the type of filter (kinds of frequencies the circuit filters out) analytically

2. The attempt at a solution
I believe the top filter to be an inverting low-pass filter, which passes lower frequencies and blocks higher frequency signals. I also think that the bottom filter is an inverting band-pass filter, blocking both higher and lower frequencies and allowing a small range through. The last stage is an inverting summing amplifier, adding the two signals together at the end.

Overall, the circuit passes both a middle and lower range of frequencies, but blocks the higher range, if I am correct in my thinking. That would make it a band reject filter, right? Since it only blocks higher frequencies but allows mid- and low to get through?

I'm not entirely sure I'm correct about the type of filters, any help would be nice!

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bran_1 said:
I believe the top filter to be an inverting low-pass filter, which passes lower frequencies and blocks higher frequency signals. I also think that the bottom filter is an inverting band-pass filter, blocking both higher and lower frequencies and allowing a small range through. The last stage is an inverting summing amplifier, adding the two signals together at the end.
Seems right to me too.
bran_1 said:
Overall, the circuit passes both a middle and lower range of frequencies, but blocks the higher range, if I am correct in my thinking. That would make it a band reject filter, right? Since it only blocks higher frequencies but allows mid- and low to get through?
I don't think I'd call it a Band-Reject filter. I usually think of a Notch filter as a band reject filter, and this is not a notch filter. It seems more like a bandpass filter with faster rolloff at the low frequencies. But without values for the resistors and capacitors in the circuit, it's hard to go much further, IMO...

berkeman said:
Seems right to me too.

I don't think I'd call it a Band-Reject filter. I usually think of a Notch filter as a band reject filter, and this is not a notch filter. It seems more like a bandpass filter with faster rolloff at the low frequencies. But without values for the resistors and capacitors in the circuit, it's hard to go much further, IMO...

Sorry, forgot to include those!

R1 = 1ohm
R2 = 1ohm
R4 =1ohm
C1=5mf
C2 = 2mf
C3 = 2mf

Edit: how would the values affect the functionality of the setup though? Wouldn't it still act the same way for certain frequencies?

bran_1 said:
Edit: how would the values affect the functionality of the setup though? Wouldn't it still act the same way for certain frequencies?
Do you have access to SPICE to plot this circuit's frequency response? If not, can you calculate the 3dB inflection points for the transfer functions of the two filters?

berkeman said:
Do you have access to SPICE to plot this circuit's frequency response? If not, can you calculate the 3dB inflection points for the transfer functions of the two filters?
I do, however apparently I'm supposed to be able to determine what kind of filter it is analytically, without having to go through all the calculations.

## 1. What is a filter type?

A filter type refers to the classification of a filter based on its characteristics and how it processes input data.

## 2. How do you identify the filter type?

To identify the filter type, you need to analyze the input and output signals of the filter and determine its frequency response, transfer function, and impulse response.

## 3. What are the common types of filters?

The common types of filters include low-pass, high-pass, band-pass, band-stop, and all-pass filters. These filters have different frequency response characteristics and are used for different purposes.

## 4. What are the differences between analog and digital filters?

Analog filters process continuous signals, while digital filters process discrete signals. Analog filters use electronic components, while digital filters use algorithms and software. Additionally, digital filters offer better precision and flexibility compared to analog filters.

## 5. Which filter type should I use for my application?

The choice of filter type depends on the specific requirements of your application. Low-pass filters are used to remove high-frequency noise, while high-pass filters are used to remove low-frequency noise. Band-pass filters are used to isolate a specific frequency range, and band-stop filters are used to eliminate a specific frequency range. All-pass filters are used for phase correction and time delay compensation.

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