gyratorinductanceinductorsimulated
I am studying the construction of some touch sensors, and I need inductances of 10mH, I know I can easily do it, and also purchase them without much difficulty, however I know that it is possible to simulate such inductances using a circuit called Gyrator.
What would be the pros and cons of replacing a passive inductor by a simulated inductor with Gyrator.
You appear to be talking about these two variants: -
Both are equally good but you will find that for low frequencies of cut-off (such as audio) the parallel output inductor becomes too physically big compared against a series capacitor. Just try calculating a 100 Hz filter with a 1 kohm resistor.
The capacitor should have a reactance of 1000 ohms at 100 Hz hence, it has a value of 1.6 uF. The inductor also has a reactance of 1000 ohms and therefore has a value of 1.6 henries and will be bulky in comparison, have an annoying self resonant frequency in the kHz region and will cost possible 100 times more than the capacitor.
If you are thinking about a much lower impedance then things change; if R is now 10 ohms, L would be 16 mH and C would be 160 uF i.e. a less clear-cut differentiation.
Go do some math and look up inductors at distributors websites.
Exactly the same argument applies to low pass filters because the same components are used but the output for low-pass is taken across the "other" component: -
You're not meant to have 2 independent sources working at the same time in the circuit, so the best way to deal with this is to use source transformation which will produce a voltage source making the circuit a combination of 2 voltage sources. I'm not sure it can be solved otherwise. Besides before you solve for neper frequency the RLC circuit has to be either a completely parallel or series circuit. Your circuit above is neither (series-parallel), to find 'alpha' you have to use source transform to make it a completely series circuit.
Best Answer
The major disadvantage of a gyrator is that it needs DC power and a DC bias to set the circuit up correctly. The advantage of an inductor of course is that this is not needed.
Another disadvantage of a gyrator is that they are all (from what I've seen of the simple transistor/op-amp type) all ground referenced at one end of the inductor i.e. if you wanted an inductor that was ungrounded on both pins then it becomes a lot more complex.
Many inductors are used in power applications (such as switch mode power supplies). In simple words, gyrators are useless in these applications.
The main area that I see a lot of gyrators used is in audio graphic equalizers where a low power and low to medium Q factor is needed. Also frequencies are moderately low i.e. limited to no-more than 20kHz.