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Old November 18th 07, 10:56 PM posted to rec.radio.amateur.antenna
Roy Lewallen Roy Lewallen is offline
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First recorded activity by RadioBanter: Jun 2006
Posts: 1,374
Default Resontate frequency of parallel L/C

Dave wrote:
Roy Lewallen wrote:
Is this by any chance an exam question?


No, it is not. I was shown it by a lecturer of mine more than 10 years
ago. The result is quite interesting.


With the given values, it's a constant-impedance network. I've used one
many times in time domain circuit designs. Its impedance is a constant
real value of 1000 ohms at all frequencies. Since "resonance" implies a
single frequency (at which the reactance is zero), this circuit isn't
resonant at any frequency. The circuit is often used in time domain
applications (e.g., oscilloscopes) where it's sometimes necessary to
provide a constant impedance load but you're stuck with a capacitive
device input impedance. In that situation, the C is the input C of the
device. However, the transfer function isn't flat with frequency-- you
end up with a single pole lowpass rolloff, dictated by the R and C values.

For anyone who cares about such matters, "resonate" is a verb,
"resonant" is the adjective, and "resonance" the noun. A resonant
circuit resonates at resonance.

Roy Lewallen, W7EL