[Homework] Identify Filter type

[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!

 

[berkeman]

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.

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...

 

[bran_1]

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?

 

[berkeman]

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?

 

[bran_1]

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.