How to determine Q from a graph?

JoeBob · 13th November 2004, 02:56 AM

I've got a graph plotting the amplitude of a signal with respect to frequency. It's just a simple bandpass RLC circuit. My question is how do I determine the Q of the circuit if the value of the resistor is unknown? I just can't remember how, a quick jog of my memory should be all it takes. Thanks...

Sch3mat1c · 13th November 2004, 03:45 AM

Something to do with width of the -3dB passband, for sure...

I don't remember what the figures are. If I ever knew.

Tim

Bill Fitzpatrick · 13th November 2004, 04:01 AM

I don't know why we have to perform the google searches for you.

http://www.st-andrews.ac.uk/~www_pa/...pt3/expt3.html

JoeBob · 13th November 2004, 04:05 AM

Well, I did do a google search, I guess I just didn't search for the right keywords. Thanks alot for the link though.

Bill Fitzpatrick · 13th November 2004, 04:12 AM

Stick this in your library of google search hints.

"circuit q" rlc

13th November 2004, 02:56 AM	#1
JoeBob diyAudio Member Join Date: Nov 2001 Location: Montreal, Canada	How to determine Q from a graph? I've got a graph plotting the amplitude of a signal with respect to frequency. It's just a simple bandpass RLC circuit. My question is how do I determine the Q of the circuit if the value of the resistor is unknown? I just can't remember how, a quick jog of my memory should be all it takes. Thanks...

13th November 2004, 03:45 AM	#2
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	Something to do with width of the -3dB passband, for sure... I don't remember what the figures are. If I ever knew. Tim __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"

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13th November 2004, 04:01 AM	#3
Bill Fitzpatrick diyAudio Member Join Date: Jun 2001 Location: Eugene, OR	I don't know why we have to perform the google searches for you. http://www.st-andrews.ac.uk/~www_pa/...pt3/expt3.html

13th November 2004, 04:05 AM	#4
JoeBob diyAudio Member Join Date: Nov 2001 Location: Montreal, Canada	Well, I did do a google search, I guess I just didn't search for the right keywords. Thanks alot for the link though.

13th November 2004, 04:12 AM	#5
Bill Fitzpatrick diyAudio Member Join Date: Jun 2001 Location: Eugene, OR	Stick this in your library of google search hints. "circuit q" rlc

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