Inductors and op-amps ?

Thread Starter

DarthVolta

Joined Jan 27, 2015
149
I know the basics of inductors and op-amps, why are inductors so rarely used in op-amp circuits ? I can't really remember any circuit besides an LC tank oscillator's, that use them ?? Even in "compensation" circuit's I've worked on, they'll have an RC network, but no inductor's.
 

danadak

Joined Mar 10, 2018
3,612
Because with OpAmps and C's we can create a circuit, filter for example, whose response
looks like it has L's in it. Inductors are bulky, costly compared to R & C.


Regards, Dana.
 

MisterBill2

Joined Jan 23, 2018
4,051
Another reason why inductors are not used is that at the lower frequencies, especially audio frequencies, inductors are physically large, much bigger than the resistors and capacitors. Besides that, they cost more. So in addition to the reasons given in post #2, which are certainly correct, we have these 2 additional reasons. And then one more problem with many forms of inductors is that they will pick up noise from any magnetic field that has lines of magnetic flux passing through the inductor. So there are the reasons why they are not used as much.
 

DickCappels

Joined Aug 21, 2008
5,943
Inductors are lossy and bulky while capacitors can be high Q and compact, and much less expensive.

One engineer I knew refused to use inductors even in video filter applications (in the mid-1980's when op amps did not yet work at video frequencies) because he was afraid of magnetically induced interference being picked up by them.
 

crutschow

Joined Mar 14, 2008
23,518
There is an opamp circuit configuration called a Gyrator, that emulates an inductor using resistors and capacitors.
It's sometimes used to create audio notch and other types of low-frequency filters.
 

AnalogKid

Joined Aug 1, 2013
8,143
Of the three basic passive electronic components, inductors are the hardest to produce in high volume with tight accuracy.

Also, they do not hold to true inductive characteristics over a wide frequency range. In other words, a real-world inductor is a lot farther away from a theoretically perfect inductor than real-world capacitors and resistors are from their theoretically perfect counterparts.

Also they are relatively large, heavy, and expensive.

For all of these reasons and more, designers have developed circuit techniques that achieve the desired results without using an inductor - even when an inductor is the perfect part for the job. A gyrator circuit is a good example of this.

ak
 
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