Monolithic Power Systems, Inc. (NASDAQ: MPWR) finished Monday’s session (December 22, 2025) modestly higher, closing at $945.16—up 0.86% on the day—after a notably volatile intraday swing that saw the stock trade as high as $976.05 and as low as $937.10. As of early evening trading, after-hours action was essentially flat, with the stock still quoted at $945.16 around 6:15 p.m. ET. 1
The headline context behind MPWR’s Monday spotlight: its addition to the Nasdaq-100 became effective prior to today’s market open, a structural catalyst that can reshape short-term flows, liquidity, and investor attention—especially during a holiday-shortened week when trading conditions can amplify moves. 2
Below is what happened after the bell today—and what investors will want on their radar before the U.S. market opens Tuesday, December 23, 2025.
MPWR after the bell today: the closing numbers that mattered
MPWR close (Dec. 22): $945.16 (+0.86%)
Day range: $937.10 – $976.05
Volume: ~552,992 shares
After-hours (6:15 p.m. ET): $945.16 (flat vs. close) 1
Two details stand out in that tape:
- A wide intraday range: the stock opened elevated, tagged the day’s high early, then slid toward the low-$940s before settling near $945. 1
- Volume was comparatively light versus Friday’s session (Dec. 19), when shares traded in the millions—often the kind of “mechanical-volume” backdrop you see around index events and major derivatives expirations. 1
Why Monolithic Power Systems stock was in focus today: Nasdaq-100 inclusion is now live
MPWR is now officially part of the Nasdaq-100 following the index’s annual reconstitution, which added six companies and removed six others, effective prior to market open on Monday, Dec. 22, 2025. MPWR was named among the additions alongside Alnylam (ALNY), Ferrovial (FER), Insmed (INSM), Seagate (STX), and Western Digital (WDC), while Biogen (BIIB), CDW (CDW), GlobalFoundries (GFS), lululemon (LULU), ON Semiconductor (ON), and The Trade Desk (TTD) were listed among removals. 2
Market data feeds and financial news services flagged MPWR’s Nasdaq-100 entry again Monday morning—because today is when the change becomes “real” in the index itself, with downstream implications for index-linked strategies and benchmark-aware institutional positioning. 3
Why this matters in the real world (especially in thin holiday liquidity)
Nasdaq-100 inclusion can matter for MPWR in three practical ways:
- Visibility and benchmark relevance: Being in a major index can expand the natural investor base tracking or benchmarking to it. 4
- Potential passive/quant flows: Funds and products tied to the Nasdaq-100 can drive incremental demand as they adjust holdings (often concentrated around reconstitution timing). 4
- Short-term volatility risk: Index events can create “one-off” price pressure that doesn’t necessarily reflect fundamentals—particularly when liquidity is thinner than normal. 5
Investing.com also noted the reconstitution’s December timing alongside the quarter’s “quadruple witch” expiration Friday, a setup that can concentrate rebalancing-related trading into a narrow window. 4
The bigger market backdrop: tech and semis had the wind at their back
MPWR traded into a generally constructive risk backdrop. Reuters reported U.S. stocks started the holiday-shortened week higher, with technology and AI-linked shares helping support sentiment and the Philadelphia Semiconductor Index rising on the day. 5
This matters for MPWR because it tends to trade with the broader “AI infrastructure / high-performance semis” narrative—especially after Monolithic has highlighted AI-related demand drivers in recent quarters. 6
Fundamental checklist: the latest company signals investors keep coming back to
Even on a day dominated by index mechanics, investors still anchor to fundamentals—particularly for a premium-valued semiconductor name.
1) Dividend clock: next key dates are approaching fast
Monolithic Power Systems announced a fourth-quarter dividend of $1.56 per share, payable January 15, 2026, to stockholders of record as of December 31, 2025. 7
Some market calendars list an ex-dividend date around Dec. 30, 2025 (timing can depend on settlement conventions and exchange schedules), so income-focused holders often keep an eye on the final week of December for positioning. 3
2) The most recent outlook: Q4 revenue guidance tied to AI demand
In its late-October update, Monolithic projected fourth-quarter sales between $730 million and $750 million, above analyst consensus at the time, with Reuters explicitly tying the outlook to an “AI boost.” 6
This is one reason MPWR is often categorized as an “AI picks-and-shovels” semiconductor play: power management is a critical layer in servers and accelerated computing platforms, and incremental demand can show up even when the earnings calendar is quiet.
3) Current valuation snapshot (context, not a verdict)
As of the latest consolidated quote, MPWR’s market cap sat around $44.1 billion with a trailing P/E near 23.3 (data-provider dependent).
Analyst forecasts and Street sentiment: what’s “in the air” heading into Tuesday
While there was no fresh earnings release today, recent Street commentary still shapes positioning—especially after a major index change brings new eyes to the name.
Recent notable analyst move
Market news services have highlighted Truist’s recent action on MPWR, raising its price target to $1,375 from $1,163 while maintaining a Buy rating (published late last week). 8
“Consensus” expectations: still broadly constructive, but targets vary
Different aggregation services show different target averages and analyst counts (because they pull from different universes and update frequencies). One widely used market summary set the average target price around $1,196 with a “Buy” consensus across roughly the mid-teens in analyst coverage. 3
The key takeaway for Tuesday: there’s still meaningful implied upside in many published targets, but the spread between targets reflects the core debate—how durable AI-driven demand stays, how margins hold up, and how much premium valuation investors will tolerate if macro data surprises.
What to watch before the market opens tomorrow (Tuesday, Dec. 23, 2025)
This is the part that can matter more than any single after-hours tick: Tuesday morning brings macro releases that often move yields, the U.S. dollar, and high-multiple tech/semiconductors.
1) High-impact U.S. economic data due Tuesday morning
Investing.com’s Tuesday preview listed a heavy slate of U.S. releases, including:
- 8:30 a.m. ET – GDP (Q3) (delayed report)
- 8:30 a.m. ET – Durable Goods Orders
- 8:30 a.m. ET – Core PCE Price Index (the Fed’s preferred inflation gauge)
- 10:00 a.m. ET – Conference Board Consumer Confidence
- 3:00 p.m. ET – New Home Sales 9
Why MPWR investors care: “duration” equities—often including quality growth semis—can react sharply to changes in rate expectations and inflation prints, even when company-specific news is absent.
2) Holiday week market structure: liquidity and timing risks increase
Reuters emphasized that light trading conditions were expected into Christmas. 5
And the official exchange calendars confirm the practical reality:
- Wednesday, Dec. 24, 2025: U.S. equities markets close early at 1:00 p.m. ET
- Thursday, Dec. 25, 2025: U.S. markets closed for Christmas 10
In thin conditions, it doesn’t take much order flow to move prices—good to remember if MPWR gaps up or down premarket Tuesday.
3) Nasdaq-100 “aftereffects”: watch for follow-through (or reversal)
Even if the major mechanical rebalancing was concentrated earlier (often around the reconstitution window), traders frequently look for a second-day pattern:
- Follow-through buying (if benchmark demand is still completing)
- “Sell-the-news” reversal (if fast money bought ahead of inclusion and exits after the event)
Today’s intraday fade from the highs—followed by a close near $945—keeps both scenarios in play. 1
Key price levels traders are likely to reference Tuesday
Without turning this into a “signals” piece, two levels are obvious simply from today’s tape:
- Near-term resistance: the $976 area (today’s high)
- Near-term support: the $937 area (today’s low and a zone that also shows up repeatedly in recent closes) 1
Zooming out, MPWR remains well below its late-October peak: StockAnalysis’ historical data shows the stock traded as high as $1,123.38 on Oct. 29, 2025. That leaves MPWR roughly 16% below that high even after today’s gain. 1
Bottom line for MPWR stock heading into Tuesday’s open
After Monday’s closing bell, Monolithic Power Systems stock is steady, digesting its Nasdaq-100 inclusion with a modest gain and muted after-hours action. The biggest near-term swing factor for Tuesday likely won’t be an MPWR headline—it will be macro data at 8:30 a.m. ET and how markets interpret growth and inflation signals into a holiday-shortened week. 9
If you’re tracking MPWR into the Dec. 23 session, the practical checklist is straightforward:
- Watch premarket reaction to GDP/durables/PCE
- Expect holiday liquidity to magnify moves
- Keep the Nasdaq-100 inclusion flow narrative in mind
- Don’t forget the $1.56 dividend timeline as year-end approaches 7
