Clean Power for an LNA? - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: March 31, 2025, 09:38:20 pm
content: HiI use multiple LNA like this (I dont know yet since the are still in the Box):https://gpio.com/collections/low-noise-amplifiers/products/low-noise-amplifier-10-2000-mhz-usb-powered-with-gain-20-db-and-0-5-db-noise-figureThe need 5V. The "problem" is the need some clean Power if not the introduce maybe Noise.I need them as an Din Rail Adapter with higher Temp Range.I saw 2 interresting one:https://catalog.weidmueller.com/procat/Product.jsp;jsessionid=?productId=(%5b1478210000%5d)&page=ProductThere is a cheaper one:https://industrial.omron.eu/en/products/S8VK-G01505What Power Supply design is better? Or are there some better one?For other USB Stuff to power in an Enclosure I also need 5V to power them. I dont want use the "original" Adapter since the are not design for that environment.Thanks

author: Kean
author_rank: Unknown
timestamp: March 31, 2025, 10:29:46 pm
content: Those LNAs are designed for USB power, so presumably they have a reasonably good PSRR.I'd just try them on a DIN rail PSU and take some measurements of the output with an SA. Maybe use separate power supplies for any other noisy USB stuff.Meanwell have a similar DIN rail PSU the HDR-15 with -30-+70C rating. I've used the older DR-15 but not specifically with an LNA. I doubt the ones you linked are significantly less noisy, but they are possibly better built (with a reflection in price).

author: A.Z.
author_rank: Super Contributor
timestamp: April 01, 2025, 08:33:16 am
content: Seconded, USB power isn't (usually) so "clean"

author: ftg
author_rank: Frequent Contributor
timestamp: April 01, 2025, 09:21:49 am
content: Those gpio.com units seem to use PGA-103+ from Mini-Circuits.It can be run on both 5V or 3V, so it is possible that they put in a linear regulator to clean up USB noise.But it is equally possible that they saved those cents and just filtered USB power with an inductor.https://www.minicircuits.com/pdfs/PGA-103+.pdf

author: mtwieg
author_rank: Frequent Contributor
timestamp: April 01, 2025, 12:16:14 pm
content: Quote from: ftg on April 01, 2025, 09:21:49 amPossibly, but I would suspect such components to be located outside the shield can. The photos don't show any components outside the shield, so I wouldn't expect such methods to work very well (not at VHF or beyond, anyways).

author: ftg
author_rank: Frequent Contributor
timestamp: April 01, 2025, 12:45:20 pm
content: For additional fun, notice how the linked PGA-103+ using LNA does not say "Unconditionally stable", unlike this other product from them with the same MMIC.https://gpio.com/products/ultra-low-noise-amplifier-pga-103-2-ghz-unconditionally-stable-gain-20dbThey explicitly mention the "Low Frequency Stabilization Circuit", which the PGA-103+ datasheet also mentions.Because PGA-103+ is not unconditionally stable, unlike most modern MMIC's.

author: polcad
author_rank: Contributor
timestamp: April 01, 2025, 02:41:37 pm
content: I frankly doubt these LNAs have a good PSRR. They will have just a resistor or inductor for power supply filtering and nothing more.You do not say what you intend to use these LNAs for but the power supply you linked to is a switch mode. It will have a lot of noise. And do not count on the LNA to be able to suppress that. I would look for a power supply with a transformer. IT will be much larger than the one you linked to. Or add a custom filter board between you power supply and your LNA which you can also use to split the voltage to your LNAs. Another option is to look for a 12V supply and add an external board with a linear voltage regulator 12V to 5V and then distribute the power to your LNAs.

author: rf-fil
author_rank: Regular Contributor
timestamp: April 01, 2025, 10:07:49 pm
content: Both of these DIN supplies have similar ripple spec... so, no difference.An RF LNA like this won't have any PSRR. It's not an opamp. The current best practice is to use a low noise LDO to clean-up an external source. I'd pick something like TPS7A20 and chuck it on a small PCB close to the LNA.

author: radiolistener
author_rank: Super Contributor
timestamp: April 01, 2025, 10:35:38 pm
content: Quote from: Lord of nothing on March 31, 2025, 09:38:20 pm$39.00... omgits real cost is max 1 USD include PCB and shield cover, or 3 USD with the greedy seller's margin.on aliexpress you can buy it at about 3-4 USD include shipment. And a dozen of MMIC for 3-5 USD for replacement, because they are burn very quickly from static electricity and pulses.

author: radiolistener
author_rank: Super Contributor
timestamp: April 01, 2025, 10:45:16 pm
content: Quote from: rf-fil on April 01, 2025, 10:07:49 pmI'm afraid it may not be enough, some of these MMIC may consume up to 400-500 mA and may heat a lot, so there is a sense for a good heatsink, especially these which needs 5V power supply

author: ftg
author_rank: Frequent Contributor
timestamp: April 02, 2025, 07:30:55 am
content: According to the datasheet, the max current consumed by PGA-103+ is 120mA.So at least this MMIC would be within the capabilities of the TPS7A20.

author: radiolistener
author_rank: Super Contributor
timestamp: April 02, 2025, 11:53:21 pm
content: Quote from: ftg on April 02, 2025, 07:30:55 amYes, that's correct. However, this specification applies to genuine MMICs. Many of the MMIC available today are Chinese counterfeits, which, although not necessarily poor in performance and maintaining decent noise figures, may draw significantly more current. These counterfeit versions could require additional cooling, such as a heatsink, to prevent overheating.In the module I purchased, the original MMIC consumed around 120-130mA, which was approximately within the specified range. I'm not sure if it was a genuine part, but it burned out quickly. I bought replacement chips from different sellers (the price was about 4 USD for dozen of chips), and all of them consumed over 250mA, with some even drawing more than 400mA. One seller sold them for about 10 USD for dozen chips, but they also consume too much current. This led to significant heating of the thick, massive metal enclosure in which my LNA is mounted. But they working ok and has the same gain.As I remember, some amateur radio enthusiasts suggested that applying a small DC bias at the input could help reduce the current consumption. However, I have not tried this approach myself.

author: ftg
author_rank: Frequent Contributor
timestamp: April 03, 2025, 07:55:18 am
content: 4usd for 12pcs of PGA-103+ sure does too good to be true.Especially when Digikey asks €2.12520/pcs even in 500pcs volume and Mini-Circuits themselves ask $1.92/pcs in 500pcs volume.Me and friends have also experienced MMIC's from china to die when run within the datasheet limits.So now I either buy them from Digikey or Mouser, or skip the middle man and desolder them myself from ewaste.In anycase, I would expect the GPIO.com to use genuine parts at their price point, especially when they are a western vendor and often explicitly stating that the product has a Mini-Circuits PGA-103+ in them.

author: radiolistener
author_rank: Super Contributor
timestamp: April 03, 2025, 07:57:55 am
content: Quote from: ftg on April 03, 2025, 07:55:18 amfor 10pcs. They are hot, but working not bad and cheaper than in branded shops

author: cncjerry
author_rank: Unknown
timestamp: April 03, 2025, 07:02:59 pm
content: We tested Lt3045 regulator modules extensively to power the DUT and various LNAs for phase noise testing. Adding them after existing DC power supplies like Tek lab grade, had a great impact on grid and other noise. The modules are not that expensive and come in fixed as well as variable formats. I would have to dig out the charts, I might have posted them under the phase noise testing threads, can't remember.Jerry

author: polcad
author_rank: Contributor
timestamp: April 06, 2025, 09:26:25 am
content: Quote from: ftg on April 02, 2025, 07:30:55 amAnd that is the reason why nobody should you those MMIC amplifiers. They do nothing but draw lots of current. Use a transistor. It is not more difficult.