For anyone starting their investing journey with just $100, there are several ways to put that money to use and build wealth. One of those ways is to buy shares of great companies and hold them for the long run. Thanks to fractional share investing, even investors with limited sources can start building diversified portfolios. It's always a good idea to diversify when investing to avoid the pitfalls of putting all your eggs in one basket.

But if you had to buy just one stock with $100, Cirrus Logic (NASDAQ:CRUS) looks like a great option. Shares of the Apple (NASDAQ:AAPL) supplier have gained impressive momentum since the beginning of May, and are now trading at around $85. Now might be a good time to buy this semiconductor stock, as it is showing signs of turning out to be a long-term play. Here's why.

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The Apple connection

Cirrus Logic gets most of its revenue from selling audio chips that are deployed in various Apple products, such as iPhones and iPads. In Q4 FY21, Apple accounted for 76% of its total revenue. Apple's share of Cirrus' business for fiscal 2021 was even bigger at 83%. Such massive reliance on a single customer isn't ideal, but the chipmaker stands to gain big from Apple's growth, and the iPhone 12's sales success has rubbed off positively on Cirrus' financials.

Apple has reportedly sold 100 million units of the iPhone 12 series in just seven months since its launch, according to Counterpoint Research, and iPhone 12 sales are tracking ahead of the initial sales performance of the iPhone 6. The additions of 5G technology and OLED (organic light-emitting diode) displays to the latest devices have triggered a second upgrade cycle for Apple customers, six years after the iPhone 6 triggered the first one. And the good news for Cirrus is that the latest upgrade cycle has just begun.

Counterpoint Research points out that the iPhone 12's share of Apple's installed base of smartphone users stood at 16% in the first quarter of 2021. For comparison, the iPhone 11 had a 25% share of the installed base, followed by older models such as the iPhone XR, iPhone 8, and the iPhone 7. So the 5G-enabled iPhone 12 ranks much lower than its older counterparts, and only has a small share of the 1 billion-strong iPhone installed base.

With more than 80% of the iPhone installed base having yet to upgrade to a 5G device, Apple looks set for multi-year sales growth. JPMorgan expects Apple to sell 226 million iPhones in 2022, compared to the lower investor expectation of 210 million to 215 million units. What's more, the upgrade cycle is likely to get a shot in the arm this year. Rumor has it that Apple could add new features to the upcoming iPhone models, such as a high-refresh-rate display, bigger cameras, and a better battery.

All of this indicates that Cirrus' dependence on Apple for a big chunk of its revenue is going to be a tailwind. However, this is not the only reason you should be considering this stock.

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The bigger play

Cirrus Logic has been working hard to diversify its revenue stream, and has already been seeing some success, with revenue from the high-performance mixed-signal solutions segment jumping 41% year over year last quarter to $57.7 million. That segment's revenue accounted for almost 20% of Cirrus' total revenue in Q4, compared to 14% in the year-ago period.

The strong performance of the mixed-signal solutions business was a boon for a Cirrus in Q4. It helped mitigate the impact of seasonality in the smartphone business, as well as a global chip shortage that restricted overall revenue growth to just 5% year over year (hitting $294 million).

More importantly, Cirrus investors can expect mixed-signal solutions to keep growing at a strong pace in the coming years. The company sees a serviceable addressable market of $2 billion in that segment by 2024, up from just $240 million a couple of years ago. The audio revenue opportunity is expected to grow 40% during that period to $3.5 billion in 2024 from $2.5 billion last year.

Even better, Cirrus has expanded its high-performance mixed-signal opportunity with its recent acquisition of Lion Semiconductor in an all-cash deal worth $335 million. The acquisition is expected to add $60 million to Cirrus' revenue this fiscal year, and immediately become accretive to the company's earnings.

The acquisition will increase Cirrus' mixed-signal revenue opportunity by as much as $1.5 billion by helping the chipmaker tap the rapidly growing fast-charging space across smartphones, laptops, and other devices. Wired and wireless fast-charging adoption has increased at a solid pace, with original equipment manufacturers pushing the envelope to boost charging speeds.

Cirrus estimates that the revenue opportunity per device equipped with fast charging could range between $0.50 to at least $2.00. Given that fast-charging has become ubiquitous in the smartphone market, Cirrus seems to have done the right thing by making a move for this space.

As such, Cirrus Logic is a play on the secular growth of the smartphone market in general and 5G devices in particular. That's why investors looking to add a potential growth stock to their portfolios should go long on Cirrus Logic -- not to mention that it's trading at 23 times trailing earnings, a discount to the S&P 500 index's multiple of nearly 38.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.