How do you calculate inductor in an amplifier?

[maniana]

Hi,
Could someone tell me what are the methods of calculating a collector (dren) inductor value in an RF power amplifier? I mean the one that connects the collector of a transistor to Vdd.
I thought I knew how to do it but yesterday some guy told me about his method, which is different than mine, and I am very confused now.

 

[vfone]

The RF Power Amplifier inductor placed between collector (or drain) and Vcc, generally is a choke. The DC resistance of this choke shall be very low, to do not affect the PA efficiency.

 

[kspalla]

It varies from point of application
Let say for DC you need choke
for in band tuning use calculations
for harmonic suppression again use calculations.
etc.

 

[maniana]

Is it still a choke in case of a wideband amplifier (LNA) ?
Someone told to pick the value of that inductor in such a way that it has the same impedance at the operating frequency as a resistor that would have been there to get Vdd/2 at the collector for a given operating point (Ic).
Say you have 12V Vdd and Ic=100mA operating point, hence Vdd/2=6V.
6V/100mA=60ohm
2*pi*f*L should be 60ohm

Is this theory wrong?
Is it still a choke in case of a wideband amplifier (LNA) ?

 

[vfone]

Especially for a wideband LNA the inductor must be a choke. Some wideband LNA applications (where power efficiency is not important) uses also a resistor in series with the choke.