How to improve amplifier IP3?

[AlexUA]

Hello everyone!

I have some question.... Could you help me?
how to improve IP3? Can we use different type of amplifier, for a example, push-pull or balanced to decrease intermodulation distortion?
:?:

 

[biff44]

Big bypass cap on the DC supply sometimes helps. Like 100 uF or so.

 

[safwatonline]

i think just increasing the Veff of the input pair this has the majour effect , plus u can use source coupled MOSTs as ur input pairs this should also enhance ur IP3

 

[RFDave]

IP3 is determined by the 3rd harmonic distortion. If you match the output so that the 3rd harmonic sees a low impedance, you should see an improvement in your IP3 performance.


Dave

 

[szekit]

there is still third order intermodulation non-linearity which is close to the input signal frequency which the low impendance path at the third order harmonic cannot get rid of..

 

[AlexUA]

Safwatonline. Hello.

Sorry, but I don’t understand fully what you mean. It's possible because of my English. Veff is voltage of DC supply? Do you suggest to spill the input power for couple MOST and amplify its separately, and after couple power at out (likely, balanced amplifier)?
If I’m wrong, can you try to explain ? thanks.

 

[safwatonline]

Veff=Vgs-Vth the overdrive voltage

i meant that u can remove the tail current source of the diff. pair and then connect the common source of the diff. pair to gnd (if they are NMOS or vdd if they are PMOS)

 

[AlexUA]

Hi
at first let me thank all of you.

...just I've heard about improving IP3 by optimization of the input and output matching circuits. Anyone know about it?