Amp Biasing With Power Reg..

[KD2GOE]

I am working on a KL503, it's a mosfet amp i use for 10 meters... I am merely using it as a simple learning tool as i start working with amps. It is a cheep amp so no crying if i blow it up.
The mod that has been done to it was eliminating the driver section of the amp and that worked out well..

Now Can i use a LM317 to set the biasing voltage of the fets? I would like to have something that would give it a more consistent voltage supply to the biasing that will not very upon loading down.

I dont see why i cant do it this way just bypass the resistors that drop the volts and use the reg to control it.

 

[vo1ks]

The bias current will vary slightly as the supply voltage changes.
You will be able to get a more stable bias voltage using the voltage regulator followed by a potentiometer. Bypass capacitors and a medium size electrolytic will help keep it more stable.

I am working on a KL503 i have, it is a mosfet amp i use for 10 meters... I am merely using it as a simple learning tool as i start working with amps. It is a cheep amp so no crying if i blow it up.
The mod that has been done to it was eliminating the driver section of the amp and that worked out well..

Now Can i use a LM317 to set the biasing voltage of the fets? I would like to have something that would give it a more consistent voltage supply to the biasing that will not very upon loading down.

I dont see why i cant do it this way just bypass the resistors that drop the volts and use the reg to control it.

 

[binrat]

There is a schematic of what to use around somewhere on the site here. I used it about 3 years ago with success.

 

[KD2GOE]

There is a schematic of what to use around somewhere on the site here. I used it about 3 years ago with success.

Where you able to fined any info on that?

 

[AudioShockwav]

Try a search using the search forums tab above.
Here are a couple things to look at.

http://www.worldwidedx.com/threads/quick-and-dirty-class-ab-mod-for-kl300p.93982/

http://www.worldwidedx.com/threads/bias-design-amplifier-design-filtering-etc.37454/

73
Jeff

 

[JoeDirt]

I am working on a KL503, it's a mosfet amp i use for 10 meters... I am merely using it as a simple learning tool as i start working with amps. It is a cheep amp so no crying if i blow it up.
The mod that has been done to it was eliminating the driver section of the amp and that worked out well..

Now Can i use a LM317 to set the biasing voltage of the fets? I would like to have something that would give it a more consistent voltage supply to the biasing that will not very upon loading down.

I dont see why i cant do it this way just bypass the resistors that drop the volts and use the reg to control it.

If your bias voltage is above 3.4v on the gate all the time you shouldn't have any issues. The KL503 is biased with zener diodes and they should work just fine with voltage fluctuation.

You can use a LM317 but I really dont think its necessarily going to be better.

I would bypass (if you havent already) the variable power. Spent your time on the input tuning.