Electronics - Operational Amplifiers - Discussion
Discussion Forum : Operational Amplifiers - General Questions (Q.No. 20)
20.
What is the cutoff frequency of this low-pass filter?


Discussion:
24 comments Page 2 of 3.
SUJI said:
10 years ago
I'm also getting 4.8 khz please explain.
Abhiee said:
10 years ago
Please explain! I am not getting correct answer.
Vikas said:
1 decade ago
My answer coming 1.8khz
Daks said:
1 decade ago
F = 1/2*pi*R*C
F = 4.8Khz.
F = 4.8Khz.
Bhaskar said:
1 decade ago
Nisha could you please tell me how can we take that the value of Pi =1.34.
Vignesh said:
1 decade ago
I think 4.8khz is correct answer. Because of LPF cutoff frequency formula is 1/2*pi*R*c.
Shobha said:
1 decade ago
Take load resistance RL = R = 10K.
Because the formula 1/(2*pi*RL*c).
Because the formula 1/(2*pi*RL*c).
Ch. Sathish Kumar said:
1 decade ago
Could you please elaborate your answers @D Sati and @Vikas. If we calculate with the formula you gave it again gives the answer as 4.8KHz. And the other thing I would like to put forth before you is that the advantage of this configuration is that the op amps high input impedance prevents excessive loading on the filters output while its low output impedance prevents the filters cutoff frequency point from being affected by changes in the impedance of the load.
D sati said:
1 decade ago
At cut off freq output of opamp should be 1/2^.5.
At frequency 0hz output is=vin
So at cutoff freq vout= vin/1.414
Because vout = vin/(r*s*C+1)
Or |v|=vin/((r*s*c)^2+1)^.5
So (r*s*c)^2=1
So r*s*C=1
So 1.8k ans.
At frequency 0hz output is=vin
So at cutoff freq vout= vin/1.414
Because vout = vin/(r*s*C+1)
Or |v|=vin/((r*s*c)^2+1)^.5
So (r*s*c)^2=1
So r*s*C=1
So 1.8k ans.
Nisha said:
1 decade ago
fc=1/(2*pi*R*C)
= 1/(2*3.14*33*10^3*0.001*10^-6)
= 4.8KHZ
= 1/(2*3.14*33*10^3*0.001*10^-6)
= 4.8KHZ
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