Design of RF Power Amplifier

[flames4791]

Hi, I need to design a power amplifier for a bluetooth transmitter. I have designed a VCO and there are simple calculations that can be made for the oscillator to achieve all the desired specifications such as sizing the transistors such that gm is larger than 1/Rp so that the gain= gmRp > 1. So my question is, what procedure or calculations should be made to design a power amplifier that meets the following specs?

supply voltage = 1v
current < 3mA
gain= 15dB
operating frequency= 2.35G to 2.55G
s22 output matching < -10dB
output power = 0dbm
output p1db = +3dbm

Any design tips or references would be greatly appreciated. Thanks!

 

[pragash]

1) select a device according to operating frequency, gain, supply voltage, power and etc.
2) plot DC characteristics and determine DC operating by using Prms = Vds x Ids. Prms is RF output power.
3) do impedance matching for the PA using commercially available matching tools (e.g ADS and etc). make sure the matching network within the Qmax circle. Q = circuit Q.
Qmax = Fo/3dB BW
Fo = centre frequency
3dB BW = 3dB bandwidth
Qmax = maximum circuit Q which meets the bandwidth


you may do loadpull to get input impedance and output impedance if you have test setup available before designing PA matching network.

 

[flames4791]

any tips on transistor sizing? also, input matching is not a required spec for my design

 

[pragash]

what do u mean by transistor sizing? are u designing MMIC PA?

input matching surely required..

 

[flames4791]

what do u mean by transistor sizing? are u designing MMIC PA?

input matching surely required..

i mean transistor sizing as in what I should be gm value and such should I try to achieve. For the VCO i sized the transistor so that the gm value was greater than 1/Rp in order to have oscillation.

I'm not sure why but my advisor said we did not need to do input matching.

 

[pragash]

then you are talking about MMIC design. im a discrete designer. someone else will answer your next questions.