Missing information on ac-ripple power noise sensitivity in TQP3M9036 and TQP3M9038

RF Solutions RF Low Noise Amplifiers
1

Hi,
I’m using two LNAs, TQP3M9036 and TQP3M9038, in my RF chain.

Both these LNAs have supply voltage of 5V with an operating margin of +/- 250 mV.

We know that LNAs are generally very sensitive to power supply ac ripple noise. However, in the data sheets of both of these devices, there is no information regarding their sensitivity to power supply ripple noise.

What is the ac-ripple tolerance in the power supply rail of these LNAs, i.e., how sensitive are these LNAs to power supply ac noise? Also, what is the frequency range of the sensitivity to power supply ripple noise?

This will help me a lot in deciding proper LDOs or ferrite bead filters for these LNAs.

Regards,
Binayak

2

Qorvo doesn’t typically characterize power supply noise sensitivity for amplifiers like this. The device will have some rejection to noise on the supply, just not quantified. It is not normally an issue when using a typical LDO and the recommended decoupling networks.

3

Hi Chris,

Thanks for your reply.

If we take TQP3M9036 as an example, the only decoupling network used in the datasheet (& EVBs) is a parallel combination of two capacitors - 1uF and 0.1nF both in 0402 package size. This looks like a bare minimum to me.

(1) Does this mean that this LNA has some more decoupling/filtering network inside the chip?

I receive 5V in my RFFE board generated from a DC/DC converter. I have two ways to reduce the ripples - either use an LDO or design a passive filter [ferrite bead (in series) + capacitor(in shunt)].
(2) Would you recommend LDO over a passive power filter network?

(3) Since you mentioned a typical LDO, can you point towards LDOs that you have in mind? The reason I’m asking is because - in the market, we can find varieties of LDOs with “low noise high PSRR” to “ultra low noise & very high PSRR” which can drive the BOM cost significantly.

Regards,
Binayak

4

I’d normally recommend a linear regulator, LDO type typically used. A low noise LDO should be fine. Alternatively a SMPS DC/DC convertor is probably OK with adequate filtering and decoupling. It depends on your application requirements and how sensitive the system is to any AM and PM noise injected from the amplifier. Typically for power supply noise you want to be down in the microvolts range. Good RF PCB layout practice also important to prevent problems, like grounding and position of decoupling. Note that I’ve never personally had a customer report a power supply noise issue affecting a Qorvo gain block or LNA.

5

Hi Chris,

Thanks for clearing that up. I’ll go with a decent low noise LDO.

Regards,
Binayak