Why we avoid inductance for low frequency designing?

[one-d]

inductance in filter

I'm studying amplifiers designing with op amp right now. when i saw filter circuits, there only capacitance were used. my lecturer said, it's because we avoid inductance for low frequency designing. he said some factor value will become great. but, i didn't understand. can anyone tell more about it.
thanks for your reply.

 

[flatulent]

Re: inductance in filter

In classical LC filters as the cutoff frequency goes down the component values get larger. Large value inductors are physically large and expensive.

In active filters only capacitors are used. Large value capacitors are small and low cost.

 

[Siniša]

Re: inductance in filter

It is "Q" factor. At low frequencies you would need large inductance values, and that would mean a lot of turns of wire resulting in high resistance as well. Q factor is ratio of reactance to resistance of this inductor, where reactance is 2ΠfL.
Higher the Q of inductor in filter and you will have sharper filter.
https://en.wikipedia.org/wiki/Inductor

 

[one-d]

inductance in filter

So it's because we'll need high inductance for high resistances, in low frequency design.
Thanks.

 

[mhtplsh]

Re: inductance in filter

Simply as the frequency decreases the inductanece value increases. At low frequencies the value of inducot becomes very high. Then the Q factor also comes in designing the inducor. If Q hv to be higher the guage of wire will be thick. So in total it becomes practicaly unviable idea. Hence resistors r used. We can any value in the same small size. 10mega ohm resistor is not bigger than 1 ohm in the same wattage.
Hope this will help u.

 

[one-d]

Re: inductance in filter

hmm that's explains again. the point is it's unpractical when it comes to physical circuit. thanks

 

[Mansour_M]

Re: inductance in filter

Hi Dear one-d!

Usually it is desirable to make inductance by combining other elements. Because inductances are not applicable in ICs and to have a great value inductance you must occupy a large area in a circuit and also the practical inductors contains unwanted loss. So it's logical to make inductance in a circuit by the means of simple, applicable, lossless elements such as OP-AMPs, Capacitors and Resistors.

Thanks!

 

[rabel126]

Re: inductance in filter

because they r expensive and bulky in size we avoid inductors in ciruit

we can make a differentiator with inductor but practically we avoid it but by interchanging hte place of capacitor and resistor in integrator we can obtain differentiator

 

[jinal patel]

Re: inductance in filter

Large value inductors are physically large and expensive.

 

[sonal]

inductance in filter

no it will u to use that of the conductuctance which r to we allow the applicable area of that can to be permitted

 

[one-d]

inductance in filter

Thanks for your replies.

One-d