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A Low-Noise Amplifier To Quantify Resistor Noise

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Noise is all around us, and while acoustic noise is easy to spot using our ears, electronic noise is far harder to quantify even with the right instruments. A spectrum analyzer is the most convenient tool for noise measurements, but also adds noise of its own to whatever signal you’re looking at. [Limpkin] has been working on measuring very small noise signals using a spectrum analyzer, and shared his results in a comprehensive blog post.

The target he set himself was to measure the noise produced by a 50 Ohm resistor, which is the impedance most commonly seen on the inputs and outputs of RF systems. The formula for Johnson-Nyquist noise power tells us that the expected noise voltage in a one-hertz bandwidth is just 0.9 nanovolts – tiny by any standard, and an order of magnitude smaller than the noise floor of a typical spectrum analyzer. [Limpkin] therefore designed an amplifier and signal buffer to crank up the noise signal by a factor of 100, using ultra-low noise op amps running off a pair of nine-volt batteries.

There was a problem with this circuit, however: any stray DC voltage present at its input would also be amplified to levels that could damage the analyzer’s sensitive input port. To prevent this, [Limpkin] decided to add a clipper circuit to his amplifier. This consists of a pair of comparators that continuously monitor the amplifier’s output voltage and disconnect it through a silicon switch if it goes beyond 200 millivolts. [Limpkin] packaged his circuit in a beautifully-machined case and ran various tests to ensure the clipper worked reliably even in the presence of fast input transients.

With the clipper in place, it was safe to run the planned noise measurements. The end result? About 0.89 nV, just as predicted by theory. Measuring nanovolt-level signals usually requires extremely accurate equipment and lots of tricks to minimize noise. Sometimes though, noise is just what you need to make a radio transmitter. Thanks for the tip, [alfonso32]!

 

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Business

Payments tech company Lightspeed Commerce conducting strategic review of business

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MONTREAL – Lightspeed Commerce Inc. says it is conducting a review of its business and operations including talks relating to a range of potential strategic alternatives.

The Montreal-based payments technology company made the comments after reports concerning a potential transaction involving the company.

Lightspeed says it periodically undertakes a review of its business and operations with a view of realizing its full potential.

A strategic review is often seen by investors as a prelude to a sale by a company.

Lightspeed says its board of directors is committed to acting in the best interests of the company and its stakeholders.

Company founder Dax Dasilva returned to the role of chief executive officer earlier this year and has been working to return the company to profitability.

This report by The Canadian Press was first published Sept. 26, 2024.

Companies in this story: (TSX:LSPD)

The Canadian Press. All rights reserved.

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Economy

Bank of Canada trying to figure out how AI might affect inflation, Macklem says

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OTTAWA – Bank of Canada governor Tiff Macklem says there is a lot of uncertainty around how artificial intelligence could affect the economy moving forward, including the labour market and price growth.

In a speech in Toronto at the Economics of Artificial Intelligence Conference, the governor said Friday that the central bank is approaching the issue cautiously to get a better understanding of how AI could affect its job of keeping inflation low and stable.

“Be wary of anyone who claims to know where AI will take us. There is too much uncertainty to be confident,” Macklem said in prepared remarks.

“We don’t know how quickly AI will continue to advance. And we don’t know the timing and extent of its economic and social impacts.”

The governor said AI has the potential of increasing labour productivity, which would raise living standards and grow the economy without boosting inflation.

In the short-term, he said investment in AI is adding to demand and could be inflationary.

However, Macklem also highlighted more pessimistic scenarios, where AI could destroy more jobs than it creates or lead to less competition rather than more.

The governor called on academics and businesses to work together to shed more light on the potential effects of AI on the economy.

“When you enter a dark room, you don’t go charging in. You cautiously feel your way around. And you try to find the light switch. That is what we are doing. What we central bankers need is more light,” he said.

This report by The Canadian Press was first published Sept. 20, 2024.

The Canadian Press. All rights reserved.

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Tech

United Airlines will offer free internet on flights using service from Elon Musk’s SpaceX

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CHICAGO (AP) — United Airlines has struck a deal with Elon Musk’s SpaceX to offer satellite-based Starlink WiFi service on flights within the next several years.

The airline said Friday the service will be free to passengers.

United said it will begin testing the service early next year and begin offering it on some flights by later in 2025.

Financial details of the deal were not disclosed.

The announcement comes as airlines rush to offer more amenities as a way to stand out when passengers pick a carrier for a trip. United’s goal is to make sitting on a plane pretty much like being on the ground when it comes to browsing the internet, streaming entertainment and playing games.

“Everything you can do on the ground, you’ll soon be able to do on board a United plane at 35,000 feet, just about anywhere in the world,” CEO Scott Kirby said in announcing the deal.

The airline says Starlink will allow passengers to get internet access even over oceans and polar regions where traditional cell or Wi-Fi signals may be weak or missing.

The Canadian Press. All rights reserved.

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