Selection of FET for PA and LNA?

[sekharareddy]

Dear all,

Can anybody tell me how to know that what type of FET(like MOSFET,LDMOS,MESFET,GaAs FET etc)suitable for which application in power amplifier design and LNA design? What is the criteria for selecting that?

Few people will use LDMOS and others will use MESFET and so on.

Can some body give me a clear picture of the FET selection?

Thanks in Adavance!!!!

Sekhar

 

[khouly]

it depends on the application output power and frequency range.

the LDMOS is used mainly in the 1 to 2 GHz Power amplifiers. they began to replace MESFETs in the range. they are mainly used in Mobile base stations.
they are avaliable to 2 300 Watt

the MESFETS and PHEMTS are used in frequency higher than 2 G Hz

about the LNA u need to select device with lower noise and this means small width and hence low power for very low nosie figures pHEMTS and Hetero-Junction MESFETS are still used. some time HBT and BJT do the job

Khouly

 

[sekharareddy]

Hello Khouly,

Thanks a lot for your reply.

Can you tell me,what are the main advantages of LDMOS over MESFETS in a particular frequency range(Suppose at 2GHz)?

 

[khouly]

high break down voltage , and this make the supply can be as high as 50 to 28 Volt, this can't be done using mesfets and for the same output power the current in LDMOS is lower than the MESFET based amps

khouly

 

[sekharareddy]

Thanks a lot!!!

Do you have any tutorial which compares various FETS?


Sekhar