Looking for MESFET Bias circuit

[PaulHolland]

Hi,

I am designing a MESFET PA for 2.5 GHz and need to know a good way to bias the gate so that I ca control the current in the drain.

I now have a negative bias circuit that makes -4 Volts and some resistors in between to control the current but I am not able to control the current correctly since it is either to low or in I descrease the voltage on the gate it drops directly to 3 A which is to much I need some 2.1 A...

It s a Highpower MESFET device...

Who can give me some usefull info, schematics ????..

Paul.

 

[VSWR]

Using Google with 'mesfet power amplifier bias' keyword search will give several hits, e.g.:

www.eetasia.com/ARTICLES/2003OCT/ A/2003OCT03_AMD_POW_AN.PDF

nds2.ir.nokia.com/downloads/aboutnokia/ research/library/electronics/ELE5.pdf

 

[AL0117]

Hi Paul,

look for the following radio amateur articles:

GaAs FET power amplifier for 13cm

hxxp://www.qsl.net/ok1cdj/dubus/9204-3.pdf

8W GaAs FET amplifier for 6cm

hxxp://www.qsl.net/ok1cdj/dubus/9203-2.pdf

In the Dubus archive you will find other interesting articles too.

rgds, Al

 

[limpek]

Hi, Your may like to look at the application note section in Califonia Eastern Lab website ( I think it is www.cel.com )

There, you will find a thick application note on MESFET biasing. Also lots of RF circuit design

 

[flatulent]

CEL has revised their web site so there are no application notes any more. Their site is also the slowest one around. It takes several minutes for each page to load when it is midnight Sunday in the US.

Another strange thing about them is their data sheets are skimpy compared to the ones from the parent company in Japan. http://www.csd-nec.com is the URL for the Japan operation.

Here is another story about CEL from one of my friends over there. For years their annually published paper catalog had data sheets for parts they did not sell. I once wondered if they were really a fake business for some Japanese intelligence agency to operate through, they were so poorly managed and operated.

 

[flyhigh]

Hi,

well some catalogue with obsolete parts are sometimes useful if you are looking for a replacement for that part - you can simulate and see how it will bahave. Sometimes it is not easy to find old catalogues. Anyway, regardless the catalogue problems, I have very good experience with CEI devices.

Flyhigh