check the PA i am doing

Dear All
i am trying to design a PA with NE651R479A for 900 Mhz with MWO

but the transistor Amp is not stable , how to stable , a power amp , specially i am doing a Class C amp

the MWO project is attached ,

thanks in advance

khouly

here it is

i donot know what did u do ? , and all other schematics is not working

khouly

Change the matching network and you can add a feedback resistor between B and C to get stablized.I deactive other simulations to run quickly.

What is the class of this PA?

it is based on class AB

the PAE reached with me about 56 to 60 % , but i am still in the frist phase , and i will begin to do layout , to implement the AMP

khouly

Pay attention to the linearity if it is a spec for the system and it seems that the gain is not that high.Maybe u need to consider change the matching network structure.

u mean change the output matching circuit , to get a higher output power , and the gain about 17 to 19 dB

khuoly

For best stability you should use RL feedback network from C to B
you can also use a series resistor in B which will of course reduce your gain.
the efficiency in real circuit also depends on what type of cap are you using at the output.

using alko caps is very helpfull which has a very low Er,ur

Mehdi

i have tried to add a R in sires with the gate , and this gave a nice results


khouly

Resistor in series with the gate is a cheap fix.
Even if this circuit is a driver, it will increase the Noise Figure and indirect the final Noise Power.
Try this matching network (beware V1 is -0.9V)