Electronics - Operational Amplifiers - Discussion


What is this circuit?

[A]. a low-pass filter
[B]. a high-pass filter
[C]. a bandpass filter
[D]. a band-stop filter

Answer: Option D


No answer description available for this question.

Shilpa Kakarla said: (Dec 15, 2010)  
Low pass filter succeeded by high pass filter in the above figure if we observe and hence according to their responses we get band stop filter's response..so ans is d

Vatsala Sharma said: (May 20, 2011)  
Low pass filter circuit is parallel to high pass filter circuit therefore this circuit behave as band stop filter.

N.S.Mahapatra said: (Jul 16, 2011)  
It's very easy to say that it should be a band stop filter.

Piyush said: (Feb 5, 2012)  

How you can say so easily without giving any explanation.

Rani said: (Oct 17, 2012)  
Whatever piyush said is correct, please give some explaination.

Padhu Ar said: (Nov 22, 2012)  
In this circuit had 2 capacitor that is input and output. That is called cc. So it works band stop filter.

Sajal said: (Oct 6, 2013)  
I think it is a narrow band pass filter. Check chapter 7 of the book 'Op-Amps and linear integrated circuits' by Ramakant A Gayakwad.

Sharath said: (Oct 21, 2013)  
If capacitor is connected to ground is called low pass filter. If resistor is connected to gnd is called high pass filter.

Madhavi said: (Dec 15, 2013)  
By observing the capacitor actions at lower frequency and higher frequency the given circuit is band pass filter.

Priya said: (Jan 15, 2014)  
I too agree with @Madhavi. It seems to be band pass filter by analyising the circuit at f=0 and f=infinity.

Vipin Kumar said: (Jun 9, 2014)  
This is narrow band pass filter.

Sanjivani said: (Jun 27, 2014)  
At infinity all capacitors are open so it will give output and at 0 all capacitors are short circuited so then also it will give output so we call it that it is bandstop filter.

Kumar Rahul said: (Feb 4, 2015)  
At angular frequency = 0 capacitor behaves like open circuit but shows some output values. So low pass filter and at angular frequency = infinite capacitor acts as short cut and shows some output value i.e. high pass.

Conclusion: A range of frequency is rejected (band stop).

Mrigank Shubham Saxena said: (Apr 9, 2015)  
If you will calculate using KCL on the junction where R1, C2 and C1 are connected you will find a equation then replace the Vn=Vp=R4/ (R2+R4).

A band stop filter is like (C1+C2) and band pass filter is like (C1-C2).

By this you will get to know that the circuit is band stop, as the equation contains (C1+C2), if we use C1=C2, we will get Notch filter.

I have solved this, if I am wrong, correct me.

Thank you.

Venky said: (Oct 12, 2017)  
The given answer is correct because of a parallel combination of low pass filter and high pass filter. So the entire spectrum is given to both the filters. If there is an overlapping (upper cut off frequcy of lpf is greater than lower cutoff frequency of hpf) then it acts as a band stop filter.

It's not a bandpass filter because in a bandpass filter the low pass filter is followed by high pass filter (i.e, if they are cascaded or series combination) Before identifying a filter characteristics once check whether they are cascaded or in sires along with there characteristics and order.

Praveen said: (Jun 21, 2019)  
Thanks all for the explanation.

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