THS9000: variable gain

Ernst Otto

Part Number: THS9000

Tool/software:

How much can you regulate THS9000 amplifier gain? In a graph, variations between 15 and 16 dB are displayed for different bias resistor values, which is not much.
Can we reduce its gain to say 5-6 dB by increasing the bias resistor value?

5 months ago

0 Gideon Townsend 5 months ago

TI__Intellectual 1520 points

Hello,

I'm sure you could expand on its range of gain adjustment with the bias resistor, but we don't have data with those adjustments so you would have to validate yourself with these new configurations. A better way would be to add attenuators to the input and output and use one of the recommended bias resistor values.

Thanks,
Gideon

0 Ernst Otto 5 months ago in reply to Gideon Townsend

Prodigy 30 points

Thank you.
It looks like you have the same load inductance = 470 nH in your eval board circuit for all frequencies.
The inductor listed in the BOM (table 1) has a self-resonant frequency of ~350 MHz, which does not seem optimal for 446 MHz.
What inductance would you recommend for that band and what other parameters in that circuit for the above frequency band?
This is because we ordered an eval board for testing but it looks like we have to replace some components to adjust it for our band of interest.
Grateful.
Sincerely Ernst Otto

0 Gideon Townsend 5 months ago in reply to Ernst Otto

TI__Intellectual 1520 points

Hi Ernst,

From this plot in the datasheet, on page 4, you can see the S21 with inductor value:

For 446 MHz, try a 68 nH inductor. This one from coilcraft should work: 0805CS-680XGRC

Thanks,
Gideon

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THS9000: variable gain