Variable gain amplifier at 950 MHz or wideband application for WCDMA signal

Hi, Meenakshi,

This is the audio forum. I will move your post to the high-speed amplifier forum.

-d2

Hello,

I've listed some Variable Gain Amplifiers which can reach about 1GHz or above:

• LMH6522 and LMH6523 (1.4GHz)
• LMH6521, and LMH6517 (1.2GHz)
• LMH6518 (0.9GHz)

Regards,

Hooman

I forgot to include the following:

• LMH6881 and LMH6882 (2.4GHz)

Regards,

Hooman

Hello Hooman,

Thanks for the suggestions. But it seems that these amplifiers are for ADC stage, after IF-down sampling. Am I correct?

I am looking for something to be used after DAC. I am using TSW34SH84 module which has some PA with attenuator which is bypassed in default setting.

Can you help me in finding out which tunable amplifiers are used in TSW34SH84?

Or any other suggestion is also appreciated.!

Thanks and best regards,

Meenakshi

Many thanks for correcting the forum address!

Hello Meenakshi,

I opened the BOM file for the TSW30SH84 and I did not find any amplifiers. 

You are correct that the LMH parts that Hooman referred to are designed to be IF frequency ADC drivers.  This does not mean they can not be used as DAC buffers. 

When I read the description for the TSW30SH84 it says that the DACs have a 1.5GSPS sample rate, but that the pattern rate is 750MSPS.  This means that the signal bandwidth should be less than 375 MHz.  If this is correct, then our IF amplifiers may be suitable for your application.

Our LMH6521 is a very high performance amplifier, the only drawback is that it is difficlut to DC couple.  Our LMH6881/2 amplifiers will pass a DC signal but they do not have the same distortion performance. 

What load condidtions do you wnat to drive with these amplifiers?  What kind of distortion performance do you require?

 I just looked at your post again.  Do you want an RF amplifier to for a signal that is centered at 950MHz? 

Hi Loren,

As I am already receiving modulated signal, I think getting a RF amplifier would be more easier, but I needed them with varying gain.

Actually TSW34SH84 have a default setting which bypasses the amplifier attenuator stage, which could allow me to control the gain. I posted a blog regarding this as follows:

http://e2e.ti.com/support/data_converters/high_speed_data_converters/f/68/t/318847.aspx

It would be best if I could enable it, but information in application note does not seem easy to follow / right, I am not sure. I could not find one capacitor on the board anywhere.

So I think tunable RF amplifier would be good to have. Any suggestions, comments from your experience are much appreciated.

Thanks,

Meenakshi

Hello Meenakshi,

For an RF amplifier with variable gain and good linearity at 950MHz I do not have any good suggestions. 

Regards,

Loren

Hi Loren!  Thanks anyways. your comments were thoughtful. I think I will try to add the provided option on transmitter first.