Power Amplifier dynamic resistance in Envelope Tracking PA

Status
Not open for further replies.
P

Politecnico

Member level 1
Joined
Aug 28, 2013
Messages
34
Helped
1
Reputation
2
Reaction score
1
Trophy points
8
Visit site
Activity points
316
Hi All

The primary simulation of Envelope Modulator (for Envelope Tracking Power Amplifier) is always done with a fixed resistor as the dynamic resistance of PA and it's normally around 5-10 Ohm.

1) How may I find that approximate resistance to be assumed as the load of the Envelope Modulator? Is there any calculation, measurement, ...?

2) Why lower Rload is mostly preferred?

Thanks a lot for any hint, in advance
Politecnico
 

SunnySkyguy said:
Look,at VI curve of PA and load of same ESR will produce 50% modulation. Any modulation index can be used by R ratios.
Click to expand...

Actually, I read somewhere that we can divide Vdd by Idd (drain's DC current consumption) at PA's compression point. Is that a valid statement?
 

Politecnico said:
Actually, I read somewhere that we can divide Vdd by Idd (drain's DC current consumption) at PA's compression point. Is that a valid statement?
Click to expand...
No, when biased near compression, Vdd/Idd should be quite nonlinear. At the very least, you want a load impedance equal to the slope resistance, which is not Vdd/Idd. A good simulation should use a nonlinear load derived from measurements of the PA under many operating conditions.
 
Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…