RF Choke design-Beginners questions..

[themaccabee]

Hi,

Im trying to make work an application circuit provided in the data sheet of an amplifier IC AH101.

Frequency of operation is 900MHz

The application circuit says the value of RF choke as 390nH.
I ve got a 390nH coil craft inductor saying 390nH@100MHz,Qmin 48@250MHz SFR min=560MHz, ( omitting the current requirements)

Can this inductor be used for this application??

My doubt is that since the SFR is 560MHz< operating frequency ,900MHz will it loss its inductance property??

Calculating the reactance Xl=2*pi*f*L
=2*3.14*900*390e-9
=2204.28 Ohms
I hope this will be the impedance the choke offers at 900MHz so comparing with a 50Ω load impedance , i think it will be sufficient to choke out RF signals goin into power supply rails..
But my doubt remains about SFR..
Can somebody help me please??
Regards

 

[RCinFLA]

You should be fine with that coil.

You are working against the 50 ohm termination load so any small stray capacitance beyond SRF will be minor.

Sometimes you have to think broadband to keep amplifier stable. Most of these modules are pretty stable.