Can anybody tell me the functions of each inductors used on this class C RF amp?

[Willen]

Can anybody tell me the detail functions of each inductors used on this class C RF amp?

 

[vtech]

If you study the class C operation, it would be a lot easier to understand the purpose of each device; The values are usually based on specific operating frequencies;
L1 (part of the of the input stage, mainly providing low impedance path to the base of transistor.--best to use an addditional capacitor in series)
L2( inductor used as high impedance to RF signal while providing zero DC bias for transistor)
L3 (used as a energy storage for the output resonance circuit during transistor OFF time)
L4 ( part of the tuned output resonance tank used to keep the output sine wave going during the non-conducting portion of the input cycle).

 

[Willen]

i think they are not very critical in their values, are they?

 

[panic mode]

wrong...
L4 for example is a part of a tuned RF circuit.

 

[vtech]

i think they are not very critical in their values, are they?

About the only one which is not single-value specific is L2, The idea there is to provide high impedance to your rf signal while providing dc ground at the base. Therefore it's value must be within a range lets say (1-100UH). Sometimes a ferrite bead will also do the job. Remember that in Class C, there is practically no DC biasing. The input signal controls the turn on/off, thereby increasing efficiency. Other coil values are infact critical and application specific.