Hi GK,
I agree with Itsu.
If we use this calculator,
https://www.redcrab-software.com/en/calculator/electrics/resistors-capacitors-inductors-series it reveals some more data, see attachment.
I used 3.54 V RMS in the calculator instead of the 10 V
p-p to get the real current of 70.8 mA, this is set entirely by the 50 Ohm internal resistance of your generator
at the series LC resonance of 19.59 kHz. (50 Ohm = 3.54V / 0.0708A)
The Q factor is very very small, 0.0738 (3.69 Ohm / 50 Ohm) hence the voltage across either L or C can only be 10V
p-p x 0.0738 = 0.738V
p-p (0.261 V RMS) at resonance.
Because the bandwidth of this LC circuit is very wide, around 265 kHz due to the very low circuit Q, it is quasi impossible to find resonant voltage peaks across either L or C.
In the video you refer to the L inductance is 220 uH (i.e. nearly 8 times higher) and his resonant frequency is around 32 kHz, so the inductive and the capacitive voltages across L and C can be higher
as seen on his scope.
Back to your circuit, if you enter 20 V into the calculator I refer to above, (remembering it is a peak to peak value) the voltages across the 30 uH and the 2.2 uF would be 1.48 V
p-p and this is
very close to that of the values Itsu measured.
PS if you use a MOSFET driver IC like say TC4420 it has a 2.5 Ohm output impedance only instead of the 50 Ohm, so the driving current to the series LC circuit can be much higher (but should be within the specs of
the TC4420 max output current rating of course).
Gyula
Author
Topic: Vector Network Analyzer and Spectrum Analyzer (Read 700 times)
