LC Band-Pass and Notch Filters

164

02:40:12

On the left is a band pass filter, and increasing the resistance of the resistor makes the filter wider while decreasing the resistor make the filter sharper. On the right is a notch filter. Increasing the resistor makes it sharper, while decreasing the resistor makes it wider. The 1uOhm resistor is just so that the AC simulation doesn’t stop after reaching the critical frequency of the notch filter. To better see the band-pass filter’s frequency response, you should get rid of the green line. The equation for the value of the damping resistor is √(L/C)* with L in Henries, C in Farads, and the result in ohms.

*Credit to @2ctiby for the sqrt symbol.

published 7 years ago

592azy2circuitdude

7 years ago

Interesting. I didn't know about the damping resistor (1uOhm). Cool

jason9

7 years ago

That’s not a damping resistor. That resistor is just to make the bode plot (frequency response chart) work right.

hurz

7 years ago

the 1uOhm resistor is a workaround for Everycircuit and its BodePlot feature.

Issacsutt

7 years ago

How do becibals work, I don't understand how much 1 or 100db is, they're logarithmic power ratios for measuring sound and amplification right? Beyond that, I don't know how to interpret them?

Issacsutt

7 years ago

Jason9, thanks for the tutorials

jason9

7 years ago

Your welcome. 0dB is 1V, -20dB is 100mV, -40dB is 10mV, -60dB is 1mV, 20dB is 10V, 40dB is 100V, 60dB is 1kV. When measuring amplification is dB, you subtract the input voltage in dB from the output voltage in dB. So, if your input is 100mV and your output is 10V, then your input is -20dB and your output is 20dB for a gain of 40dB, or you could use the bode plot and set the input to 1V (0dB) and see what it says for the output. You can convert dB to V using this equation: 10^(dB/20).

jason9

7 years ago

The equation for converting V to dB is: log₁₀(V)*20.

jason9

7 years ago

Voltage is measured in peak voltage, not peak-peak voltage, and not RMS.

Issacsutt

7 years ago

Ok thanks, very helpful! Thought it was much more complicated than that

jason9

7 years ago

Your welcome.

592azy2circuitdude

7 years ago

Oh sorry. Then the damping resistor is the 100ohm?

jason9

7 years ago

Yes

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