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Design >> RF Design >> RF Differential input Single-ended Output Amplifier
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Message started by mohammadreza on Aug 9^th, 2010, 3:36am

Title: RF Differential input Single-ended Output Amplifier
Post by mohammadreza on Aug 9^th, 2010, 3:36am

I am designing an RF PA which is almost ready. I used a VCVS to convert my differential input signal. But now, I am supposed to make an RF Amplifier as well, which doesn't necessarily amplify very much, but can convert my differential input signal to a single-ended one. What I am looking for is an inductorless type. My operating frequency is 2.4GHz, so the traditional lower frequency OpAmps don't help.

Please let me know if any idea poped into you.

Regards

Title: Re: RF Differential input Single-ended Output Amplifier
Post by RFICDUDE on Aug 10^th, 2010, 5:44pm

Yes, lots of ideas popped into my head.
:)

Title: Re: RF Differential input Single-ended Output Amplifier
Post by mohammadreza on Aug 14^th, 2010, 4:45am

so...?
:) 8-)

Title: Re: RF Differential input Single-ended Output Amplifier
Post by Ken Kundert on Aug 14^th, 2010, 9:55pm

Perhaps you should asked a specific question.

-Ken

Title: Re: RF Differential input Single-ended Output Amplifier
Post by mohammadreza on Aug 16^th, 2010, 1:49am

Actually, the what i knew was using an Op-Ampl and trying to seprate it's poles and getting small gain out of it at the intended frequency. that's practical for under 1GHz as the TI suggests but not for the 2.45GHz.

Another method is using charge pumps, but that's not helpful in ultra low power (-10dBm).

almost all I found in searching the databases is about differential low noise amplifiers whcih are either single-ended input and differential output or they are totally differential.

So, have you got any idea or any document that can link it here?

Title: Re: RF Differential input Single-ended Output Amplifier
Post by carlgrace on Aug 17^th, 2010, 6:40pm

You could try an NMOS diff pair and then just take the output from one drain. This would be very fast, but you would lose half of your gain. What linearity do you need? You said you used an op amp, but I think you will need an open-loop amplifier.

Title: Re: RF Differential input Single-ended Output Amplifier
Post by mohammadreza on Aug 18^th, 2010, 2:13am

yes, you are right, but the fact is utelizing a differential pair and even mirroring the output consumes lots of current and the poles that are created make the amplifier have a gain far below 0dB, in 2.4GHz.

But if there is a way to increase the gain and seperate the poles to very high distance and get even unity gain, that would be helpful.

But, maybe it is easier to kill one side of the input and just amplify one.

Title: Re: RF Differential input Single-ended Output Amplifier
Post by mohammadreza on Aug 18^th, 2010, 2:14am

by the way, linearity is not an issue for me. using linear class is because in the ultra low power using switches requires amplifying the signal to rail to rail which consumes more power.

Title: Re: RF Differential input Single-ended Output Amplifier
Post by rfcooltools.com on Aug 18^th, 2010, 9:54am

Diff pair to a resistor load that is differential. Then to convert to single ended try using a "totem pole circuit", you can look them up on the internet for a schematic. or you can connect to one of the resistors as suggested by carlgrace and use "white's cascode" to buffer this output.

http://rfcooltools.com