calculate the inductance used in RF choke @ 12.8MHz

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Oska

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Hi

I am design a circuit which need a inductance as a RF choke to choke the 12.8MHz signal in biasing network.

How much inductance can be take?
 

The normal purpose of a RF choke is to offer a high impedance to RF and a low impedance to DC. So it depends on your circuit. If for instance you had a RF amplifier that worked on 12V and its PA stage drew 4A DC, this would imply that the circuit impedance was ~ 3 ohms, so the choke should have an impedance of > 30 ohms at the working frequency. If you try and make the value of the RF choke too large, it then resonates with stray capacitance and becomes a tuned circuit also its DC resistance rises, so if in the example, its resistance was .5 Ohm, it would drop 2V and get hot.
Frank
 

Oska,

Be care that inductance is not the only electrical pnenomen concerned at this kind of inductors.
Saturation magnetic efect is also welcome at this case; so, high-permeability core must be considered.

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