MPWR · Monolithic Power Systems, Inc.

The thesis

Monolithic Power Systems' AI server power-chip business is running ahead of expectations, and the shares fell anyway when the whole chip sector sold off on 5 November 2026. The Q4 report, expected in early February 2027, settles the case: revenue has to reach the $1,315–1,385 million guided on 29 October 2026, and Enterprise Data has to grow from $506.7 million.

The Q3 report cleared both business tests in the previous note. Revenue was $1,202.4 million against guidance of $1,140–1,160 million, and Enterprise Data rose from $380.6 million in Q2 (company release, 29 October 2026). Rosenblatt upgraded the shares to Buy and Truist raised its target to $1,906 on 30 October 2026.

Price went the other way. The adjusted close of $1,131.43 on 5 November 2026 sits under the $1,200 weekly-close invalidation level in the previous note, and the week ends on 6 November 2026. A stronger business and a weaker share price roughly offset, so the rating is unchanged. The price test moves to a weekly close below $1,000 because the results have changed what the shares are being asked to prove.

The narrative is maturing: Enterprise Data growth has been public since the 30 July 2026 report, and a second quarter of growth above 160% did not protect the shares from the 5 November 2026 sector drop.

Bullish and bearish views on Monolithic Power Systems, Inc.

The bull case on Monolithic Power Systems, Inc. (MPWR), in brief: Enterprise Data accelerated again. The bear case: The sector can overwhelm company results.

Bull case

• Enterprise Data accelerated again. Q3 Enterprise Data revenue was $506.7 million, up 33.2% from Q2 and 164.6% year over year, and 42.1% of revenue (company release, 29 October 2026). CEO Michael Hsing said on the call that he sees no signs of a slowdown (StockStory, 30 October 2026).
• Guidance cleared consensus by a wide margin. Q4 revenue guidance of $1,315–1,385 million compares with a $1.201 billion consensus in Benzinga's 29 October 2026 headline and $1.23 billion in StockStory's 30 October 2026 review. Q3 non-GAAP earnings of $8.19 per share beat the $7.75 estimate (Benzinga).
• Growth widened beyond one segment. Communications revenue was $187.4 million, up 42.5% from Q2 and 134.7% year over year. Automotive was $180.7 million, up 15.0% from Q2 (company release, 29 October 2026).
• Analysts moved up after the report. Truist kept Buy and raised its target to $1,906 on 30 October 2026, and Rosenblatt upgraded to Buy with a $1,700 target the same day. Before the report, Wells Fargo had cut to $1,550 on 19 October 2026 and Oppenheimer to $1,500 on 23 October 2026.
• The company is buying its own shares. It repurchased $453.4 million of stock in Q3, against $4.0 million in Q2.

Bear case

• The sector can overwhelm company results. The Philadelphia Semiconductor Index fell 12.3% on 5 November 2026, its worst day since March 2020, and Monolithic fell 10.3% (Longbridge via KuCoin, 6 November 2026). Longbridge tied the drop to Qualcomm and Arm results and to analysts' concern that a Democratic Congress could make new data centers harder to build.
• Valuation remains demanding. Trefis put the shares at 69.3 times trailing earnings against 22.8 for the S&P 500 on 5 November 2026.
• Concentration is rising. Enterprise Data went from 38.8% of revenue in Q2 to 42.1% in Q3. Storage and Computing fell 3.8% from Q2 and Consumer fell 11.6% year over year (company release, 29 October 2026).
• Margins are not expanding with growth. Q4 non-GAAP gross margin guidance is 55.5–56.1%, against 55.7% in Q3 (company release, 29 October 2026). Management expects rising foundry and component costs and aims to hold 55–60% (StockStory, 30 October 2026).
• Controls and finance leadership are in flux. The 29 October 2026 release still cites the company's ability to remediate its material weakness. Company news the same day named Tony Balow chief financial officer, effective immediately, along with a new chief accounting officer.

Price setup

The adjusted close on 5 November 2026 was $1,131.43, which is 32.8% below the 52-week high of $1,684.83. The shares are down 18.0% over three months. The 14-day relative strength index (RSI, a 0–100 gauge of recent buying versus selling) is 43.8, up from 30.8 on 27 October 2026 when the close was $1,211.89.

StockStory showed the shares near $1,199 on 30 October 2026, against $1,203 before the report. Trefis measured a 14.8% decline from the 5 October 2026 close to the 4 November 2026 close, so the results arrived during a falling market for the shares.

Crowding evidence is mixed. The price is far below its high and no earnings date is near. CEO Michael Hsing sold 30,000 shares at $1,323.31–$1,356.94 on 28 September 2026 under a Rule 10b5-1 plan (Investing.com, from the Form 4), above the latest close. Tradr's 2X leveraged single-stock fund, launched 24 April 2026, can amplify daily swings. Retail attention is not measured here.

Catalysts, next 30 days

• 6 November 2026: Weekly close. It shows whether the shares ended the week above the $1,200 invalidation level in the previous note.
• ~9 November 2026, est.: Form 10-Q filing deadline for Q3 2026. It states whether the material weakness behind the 26 February 2026 non-reliance filing remains open, under a new finance chief.
• ~4 February 2027, est.: Q4 2026 report, outside the 30-day window. The case turns on it: revenue against $1,315–1,385 million and Enterprise Data against $506.7 million.

What would change the view

The case breaks if AI server demand fades in the reported numbers. Q4 revenue below the $1,315 million guidance floor would do it. So would Enterprise Data below $506.7 million, since that would end the sequential growth that carries the story.

A further non-reliance filing, or a Form 10-Q showing a wider control problem, would weaken the case for reasons unrelated to demand. Q1 2027 gross margin guidance below the 55–60% range management cited would show cost pressure outrunning pricing.

On price, a weekly close below $1,000 would end the case. It would show selling continuing well after the 5 November 2026 sector shock, despite Q4 guidance above consensus. A Q4 revenue result above $1,385 million and a filing stating the weakness is remediated would strengthen the case.

What it trades with

The shares trade with the semiconductor group more than with their own results. On 5 November 2026 Monolithic fell 10.3% against 12.3% for the Philadelphia Semiconductor Index. An investingLive recap listed the Nasdaq 100's worst day since 2020 and Monolithic among the names down 10% or more.

Twenty-eight of the 30 stocks in the iShares Semiconductor ETF were at least 20% below their record closes after that session (Longbridge via KuCoin). That follows a 15 October 2026 report of US chip stocks set to lose $2 trillion in value (Kitco). The trigger on 5 November 2026 was earnings at Qualcomm and Arm, so a sector rebound or further selling is likely to move the shares regardless of company news until the Q4 report. Moves in the shares that diverge from the index on sector news would show this view is wrong.