I setup this filter but the results I'm getting are way off from the predicted values.
V
IN_pp = 5V
V
OUT_pp at f
0 = 1.064V
R = 9.8R (measured)
L = 100uH +- 10% (marked, but not measured)
C = 1nF (marked, but not measured)
f
0 = 1/(2*pi*sqrt(LC)) = 503kHz (Calculated)
f
0 = 447.5kHz (Measured)
Q = X
L,0 / R
T = (2*pi*f
0*L) / R
T = ~32 (Calculated)
Q = 5.52 (Measured)
Bandwidth = f
0 / Q = 503kHz / 32 = 15.7kHz (Calculated)
Bandwidth = 81kHz (Measured)
I measured the resistor to get 9.8R. The cap and inductor I can't measure directly with my DMM. The inductor is marked 100uH +- 10% from digikey. The cap is marked as 1nF. I tried swapping out both the cap and inductor for components from the same package in case one of them was way out or the wrong value but the results were consistent.
My voltage source is an FG. My scope was hooked up at TP and grounded to the negative lead of the FG.
I found f
0 by sweeping the frequency until I found the maximum V
OUT_pp. I found the bandwidth by finding the frequencies below and above f
0 that produce V
OUT_PP = 0.707*V
IN_pp which was at 407kHz and 488kHz, respectively.
I'm not sure why my results are so far off. Also is my V
OUT_pp only ~1V at resonance because of the 50R output impedance of the FG (ie. voltage divider between 10R resistor and 50R FG at resonance)?
Lastly I don't see how this circuit is different from a notch filter when there is no load present? With a load they can be distinguished by whether the resistor or the LC is parallel with the load. But with no load present and an AC source I'm not sure how the two differ.