Aboutcleggsan Expertise All technical areas of Electronics Engineering.
Experience BSEE, MBA, Design, R&D, University Research.
Senior Life Member of IEEE. Life Fellow of AES.
Organizations IEEE, Consumer Electronics Society, Audio Engineering Society.
Broad teaching experience; work experience mostly in consumer electronics and conversion from analog to digital technologies. Pioneer in digital audio at all levels.
Question QUESTION: Dear Mrs cleggsan,
My supervisor has ordered me to shift my focus to passive filters. Because since im dealing with sufficiently high current system, i think that my sensing circuit is destroying my active filters. The current rating of the active filters is merely 7mA. The power supply might be giving me more whenever i on and suddenly off the power supply. May be i exceed the current rating, thats why my IC filters stop working
So, i would like to know based from your experience whether you know about any simple passive bandstop filters design that i can use to filter the harmonics?(Im working at 12V in my sensing circuit)
Thanks a lot
Diren
ANSWER: I don't remember your purpose for the filters. Could you repeat for me the purpose of the filters and why you want to filter the line harmonics? If you are just wanting to purify the power line waveform you may be able to use just a low-pass filter that passes the line frequency and rejects all harmonics. You are on a 50Hz line? Right? Then a 50Hz low-pass filter should do the job. It can be a passive network with LC components..... Let me know if I am not remembering your application clearly.
C
---------- FOLLOW-UP ----------
QUESTION: Dear Mrs cleggsan,
thanks a lot for your constructive advice. Im doing selective harmonics control in low voltage applications.im filtering the harmonics one by one at 12V.
I would like to use passive filters or some involving op-amps to filter the harmonics. Do you know any link where i can base my design?
QUESTION: Dear Mrs cleggsan,
im building a simple filter consisting of simple RLC circuits. i was looking at the datasheet of the inductive components. i was looking at the electrical characteristics of the inductor amongst which was the self resonant frequency! What does it mean 'self resonant frequency'? The self resonant frequency is in terms of MHz. im tuning my RLC circuit to go to resonance at 150Hz for instance. How does this self inductance affects the 150 Hz resonant value? (im looking at the NLV series NLV32 Type inductor)
Thanks
Answer Self resonance is when the internal capacitances of the coil itself and leads or any other nearby parts lump together to form a resonant circuit with the inductance of the coil. Or, could even be when a non-coil design has enough inductance and capacitance that can form a resonant condition. Usually at very high frequencies due to the very small values of the LC lumped properties.
Circuit designers must be aware of these as they can cause birdies or instabilities, sometimes called parasitic oscillations. Swamping them out with a cap in the right place to mitigate their effect is common place. Often you see little picofarad capacitors on schematic diagrams that you wonder what they are there for - they are often high frequency self-resonance killers.
