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[Solved] What's the Q of this circuit?
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Topic: [Solved] What's the Q of this circuit? (Read 2466 times)
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SoftwareSamurai
Regular Contributor
Posts: 170
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[Solved] What's the Q of this circuit?
«
on:
November 10, 2011, 03:49:25 pm »
While tying to learn more about bandpass filters, I stumbled across
this circuit
(see pic). Does anyone know how to calculate the Q of this filter?
I know that the addition of the Rload changes the Q, but I'm not sure how to factor both R1 and Rload into the math.
«
Last Edit: November 10, 2011, 09:15:49 pm by SoftwareSamurai
»
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Rufus
Super Contributor
Posts: 2095
Re: What's the Q of this circuit?
«
Reply #1 on:
November 10, 2011, 04:11:46 pm »
V1 has zero impedance. If you replace V1 with a line it becomes obvious that R1 and Rload are in parallel.
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jimmc
Frequent Contributor
Posts: 304
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Re: What's the Q of this circuit?
«
Reply #2 on:
November 10, 2011, 07:44:04 pm »
The resonant frequency of L1 & C1 is 159.15Hz at this frequency the reactance (X) of either is 100 Ohm.
As Rufus has said R
S
and R
L
appear in parallel so their combined resistance (R) is 333.3 Ohm.
Calculate Q as R/X = 3.333
Jim
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SoftwareSamurai
Regular Contributor
Posts: 170
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Re: What's the Q of this circuit?
«
Reply #3 on:
November 10, 2011, 09:15:23 pm »
Thanks Rufus. I hadn't thought of V1 with zero impedance. I think that's what I was missing.
Thanks Jim. I thought that Q = R/X, but I wasn't calculating R correctly which made me think that I had the wrong formula for Q.
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