generate bias voltage of power amplifier

[analog_ambi]

What is the best way to generate bias voltage VB1, VB2 and VB3?

 

[goldsmith]

What is the best way to generate bias voltage VB1, VB2 and VB3?

Hi analog_ambi
It depends on you !
Perhaps using a zener diode and then tie the biasing resistor to the supply voltage .
or if high value of DC current is required ( that won't be required for such circuit ) using a current driver or perhaps using an auxiliary DC supply .
A question :
What is application of your circuit ? is that a class E or F amplifier ? ( i've some doubts because you didn't mention anything from your outlets )
or perhaps a fast inverting system ? or perhaps an SMPS ? you should mention application of such circuit or specifications of your circuit as well , then i can guide you as well .
Best Wishes
Goldsmith

 

[analog_ambi]

This circuit will be power amplifier for ultra low power RF transmitter with EIRP=-5dBm and freq=2.4GHz. The first stage shall be class AB but the last stage is class A (cant help due to linearity requirement of modulation). Everything is integrated CMOS.

The methods suggested by u will consume lot of power! My budget is 500uW.

 

[goldsmith]

This circuit will be power amplifier for ultra low power RF transmitter with EIRP=-5dBm and freq=2.4GHz.

Hi again

may i ask you why you're not using something like Gali-5 or perhaps Gali-6 or maybe Gali-55 ? these are so good for such a purpose .

The first stage shall be class AB

May i ask you why ?

last stage is class A

You can design a class E or C or perhaps F amplifier , in linear mode ( linear in your desired range of frequency ) it is up to the designer . or using a compact amplifier like Gali series .
But if you are still interested in your circuit , you can easily handle that voltage biasing with two resistors ( two high value resistors ) to prepare the required biasing voltage . it can be obtained from each one of the available supplies in your circuit .
By the way don't forget , that you should use an RFC in this section to avoid from interferences between RF stage and DC stage .
That's all
Best Wishes + Good luck
Goldsmith

 

[analog_ambi]

goldsmith:

I am designing a cmos IC transmitter. By gali-5 do u mean discrete component? Mine is a IC design issue.

Are u sure class E , F and C can handle linearity requirement of QPSK modulation? The peak to average ratio for my case is 4dB.

 

[nitrojacob]

I am wondering, why Class AB is used in voltage amplification stage and Class A in power amplification stage? We do the opposite at audio frequencies..