What do you mean by 3 dB cutoff frequency? Why is it 3 dB, not 1 dB?

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What do you mean by 3 dB cutoff frequency? Why is it 3 dB,
not 1 dB?

Question Posted / meghana

16 Answers
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What do you mean by 3 dB cutoff frequency? Why is it 3 dB, not 1 dB?..

Answer / db

That's wrong.
3 dB implies 1/2 the power and since the power is
proportional to the square of voltage, the voltage will be
0,707 of the passband voltage.

sqrt(0.5) = 0.707

Is This Answer Correct ?

207 Yes

13 No

What do you mean by 3 dB cutoff frequency? Why is it 3 dB, not 1 dB?..

Answer / guest

It is the half power point. At this point, the
electronic/communication system has achieved the maximum
power transfer.

Is This Answer Correct ?

164 Yes

41 No

What do you mean by 3 dB cutoff frequency? Why is it 3 dB, not 1 dB?..

Answer / none

In electronics, cutoff frequency or corner frequency is the
frequency either above which or below which the power
output of a circuit, such as a line, amplifier, or
electronic filter is 1/2 the power of the passband.Because
power is proportional to the square of voltage, the voltage
signal is squere root of 1/2 of the passband voltage at the
corner frequency. Hence, the corner frequency is also known
as the −3 dB point because 1/2 is approximately −3
decibels. A bandpass circuit has two corner frequencies;
their geometric mean is called the center frequency.

Courtesy Wikipedia.

Is This Answer Correct ?

73 Yes

7 No

What do you mean by 3 dB cutoff frequency? Why is it 3 dB, not 1 dB?..

Answer / piyush

In electronics communication power gain is of great importance
ie Pout/Pin. This gain is expressed in Db ie
gain(Db)=10log10(Pout/Pin).
when the pwr ratio goes to 1/2
Pout/Pin=1/2
at this situation the the gain is -3Db beyond this the
output signal pwr falls to that extent that it becomes
useless thats why we consider 3Db cutoff frequency....

Is This Answer Correct ?

35 Yes

6 No

What do you mean by 3 dB cutoff frequency? Why is it 3 dB, not 1 dB?..

Answer / maddyavril

see we can t get the bandwidth of any amplifier u cn figure
it out wen u see a graph.so they (one who decided to use
half power point)to find the cut off freq because we need to
know about bandwidth for using it so cut off freq are needed
this cut off freq are get at 3 db point only.
y 3 db point?
is the q rite because we humans having percistence for
everything even for hearing and all we can able to sense the
change only wen the power gets at half power point . so it s
a got thearitically and kept for use 3 db point we can get
band width of amplifiers etc

Is This Answer Correct ?

26 Yes

9 No

What do you mean by 3 dB cutoff frequency? Why is it 3 dB, not 1 dB?..

Answer / hariharan

3db cut off frequency is frequency at which gain is .707 times the maximum gain.(rms value of maximum gain).

Is This Answer Correct ?

21 Yes

5 No

What do you mean by 3 dB cutoff frequency? Why is it 3 dB, not 1 dB?..

Answer / vasanthkumar.kvv

at 3dB cutoff frequency is the frequency either above or
below which the out power will become double 0r half of the
original Transmitted or received power .

eg: 50dBm =100W
3dB down is 47dBm = 50W
3dB above is 53dBm =200W
for this double 0r half power variation will start from 3dB
cutoff onwards so we will consider 3dB cutoff.

Is This Answer Correct ?

4 Yes

1 No

What do you mean by 3 dB cutoff frequency? Why is it 3 dB, not 1 dB?..

Answer / sumit

70% of the is occupied in 3db bandwidth that is why 3db band
width is take.in 3db max power become P(max)*.707. if we
take 1 db instead of 3db than power occupied will be zero
i.e. 20 log1=0.

Is This Answer Correct ?

5 Yes

5 No

What do you mean by 3 dB cutoff frequency? Why is it 3 dB, not 1 dB?..

Answer / john lam

A filter's cutoff frequency is generally defined at -3dB.
At this point, the voltage of the input has attenuated to
50%, or in power form 70.71%. After this point, the voltage
of the input will drop dramatically rendering it useless.
Therefore the -3dB point is picked as the cutoff frequency
point because of this nature. It's not chosen randomly.

Is This Answer Correct ?

1 Yes

1 No

What do you mean by 3 dB cutoff frequency? Why is it 3 dB, not 1 dB?..

Answer / rohithmc

i agree with your answers. let me take voltage as 0.6 instead of .5. now power is directly proportional to the square of voltage. i.e p=.7745. in db (20 log.7745) which is
2.2 db down point. i feel like its more appropriated than 3 db. For increase in little voltage, db is reduced. so that we can get better cut off.

Is This Answer Correct ?

2 Yes

3 No