opamp741 Quotes
WA, can u put some more light on "If the frequencies are high enough the inductor will act like a capacitor, and the capacitor will act like an inductor. " I am really not able to follow u..
I'll just go over some basics.
1. Capacitence - Current leads Voltage by 90 degrees
2. Inductance - Voltage leads Current by 90 degrees.
This is in pure circuits only. In reality though, there are other factors.
(sorry I don't have scanner so I'll explain as best as I can)
(I had to use ' because if I don't, the | won't line up (space key not recognized))
1. The practical equivalent circuit for inductance.
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'''''''''''''''''''''''''''''---[capacitance]---''''''''''''''''''''''''''''''
>--[resistor]--|--[inductance]----|---->'''''''''''''''''''
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the capacitance is in parallel with inductance.
Impedance (Z) = 2*pi*f*L
but because there is capacitence (depending on inductor value) I'll use an 10 micro henry and 100 micro henry inductor.
The resistance is the inductor resistance (wire) and the capacitence is due to the windings (space between wires)
- At 100 micro henrys the impedance peeks around 2 MHz. From 0 to 2MHz Z increases till about 2MHz. above 2MHz the inductance begins to decrease. This is because, little by little, the circuit takes on the charactistics of a capacitor.
- At 10 micro henrys the impedance peaks around 5Mhz.
2. The practical Capacitence equivelent.
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''''''''''''''[resistor1]'''''''''''''[resistor2]'''''''''''''
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The inductor are leads
The resistor1 is dielectric loss
The resistor2 is leakage (resistor2 in parallel with resistor1 and capacitance).
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Impedance (Z) =''''''''''''1'''''''''''''
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'''''''''''''''''''''''''''''''''''''2*pi*f*C'''''''
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Z starts out fairly high but decreases to zero.
(I'll use a .01 micro farad capacitor)
At around 3.5 MHz there isn't much impedance but, as freq increases above 3.5 MHz, The impedance begins to increase. This increase is because the circuit is taking on the charactistics of an inductor.
As this is a discusion topic, I'm sure other kind members can possibly provide a graph or offer better explaination than I can.
Hope this helps.
wa