Monolithic Power Systems, Inc.
MX ˙ BMV ˙ US6098391054
SecurityMX:MPWR / Monolithic Power Systems, Inc.
InstitutionCitigroup Inc
Latest Disclosed Ownership340,832 shares
Latest Disclosed Value $ 372,648,381
Citigroup Inc ownership in MPWR / Monolithic Power Systems, Inc.

On May 11, 2026 - Citigroup Inc filed a 13F-HR form disclosing ownership of 340,832 shares of Monolithic Power Systems, Inc. (MX:MPWR) valued at $372,648,381 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 13, 2026 disclosing 245,479 shares of Monolithic Power Systems, Inc.. This represents a change in shares of 38.84% during the quarter.

Citigroup Inc has a history of taking positions in derivatives of the underlying security (MPWR) in the form of stock options. The firm currently holds call options representing 0 of underlying shares valued at $0 USD and put options representing 0 of underlying shares valued at $0 USD .

Note: prior versions of this page mistakenly stated that the share values represented the number of options, not the number of underlying shares. For more information on the data backing these reports, please see the SEC document Frequently Asked Questions About Form 13F.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

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Institutional Put/Call Ratios
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In addition to reporting standard equity and debt issues, institutions with more than 100MM assets under management must also disclose their put and call option holdings. Since put options generally indicate negative sentiment, and call options indicate positive sentiment, we can get a sense of the overall institutional sentiment by plotting the ratio of puts to calls. The chart to the right plots the historical put/call ratio for this instrument.

Using Put/Call Ratio as an indicator of investor sentiment overcomes one of the key deficiencies of using total institutional ownership, which is that a significant amount of assets under management are invested passively to track indices. Passively-managed funds do not typically buy options, so the put/call ratio indicator more closely tracks the sentiment of actively-managed funds.

MX:MPWR / Monolithic Power Systems, Inc. Historical Put/Call Ratio
Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date
Effective
Date
Form Security Class ID Avg Price
Paid (Est)
Reported
Shares
ΔShares ΔShares
(%)
Reported
Value
(x1000)
ΔValue
(%)
Alloc
(%)
ΔAlloc ΔAlloc (%) Cost Basis
(x1000)
Unrealized
Gain/Loss
(x1000)
2026-05-11 2026-03-31 13F MONOLITHIC PWR SYS COM 609839105 340,832 95,353 38.84 372,648 67.49 0.0800
2026-02-13 2025-12-31 13F MONOLITHIC PWR SYS COM 609839105 245,479 67,296 37.77 222,492 35.63 0.0982
2025-11-10 2025-09-30 13F MONOLITHIC PWR SYS COM 609839105 178,183 -100,746 -36.12 164,042 -19.59 0.0731
2025-08-11 2025-06-30 13F MONOLITHIC PWR SYS COM 609839105 278,929 5,948 2.18 204,003 28.85 0.1002
2025-05-12 2025-03-31 13F MONOLITHIC PWR SYS COM 609839105 272,981 -74,199 -21.37 158,324 -22.93 0.0809
2025-02-12 2024-12-31 13F MONOLITHIC PWR SYS COM 609839105 347,180 29,692 9.35 205,427 -30.01 0.1219
2024-11-12 2024-09-30 13F MONOLITHIC PWR SYS COM 609839105 317,488 -12,344 -3.74 293,518 8.30 0.1700
2024-08-12 2024-06-30 13F MONOLITHIC PWR SYS COM 609839105 329,832 81,516 32.83 271,017 61.11 0.1736
2024-05-10 2024-03-31 13F MONOLITHIC PWR SYS COM 609839105 248,316 130,952 111.58 168,214 127.22 0.1105
2024-02-09 2023-12-31 13F MONOLITHIC PWR SYS COM 609839105 117,364 -27,245 -18.84 74,031 10.81 0.0522
2023-12-06 2023-09-30 13F/A-1 MONOLITHIC PWR SYS COM 609839105 144,609 -38,415 -20.99 66,809 -32.43 0.0499
2023-11-09 2023-09-30 13F MONOLITHIC PWR SYS COM 609839105 144,609 -38,415 66,809 0.0200
2023-08-10 2023-06-30 13F MONOLITHIC PWR SYS COM 609839105 183,024 86,480 89.58 98,875 104.61 0.0648
2023-05-11 2023-03-31 13F MONOLITHIC PWR SYS COM 609839105 96,544 12,536 14.92 48,324 62.67 0.0339
2023-02-09 2022-12-31 13F MONOLITHIC PWR SYS COM 609839105 84,008 -20,971 -19.98 29,706 -22.13 0.0237
2022-11-10 2022-09-30 13F MONOLITHIC PWR SYS COM 609839105 104,979 -28,827 -21.54 38,150 -25.76 0.0273
2022-08-10 2022-06-30 13F MONOLITHIC PWR SYS COM 609839105 133,806 -31,289 -18.95 51,386 -35.91 0.0382
2022-05-12 2022-03-31 13F MONOLITHIC PWR SYS COM 609839105 165,095 16,517 11.12 80,184 9.39 0.0487
2022-02-10 2021-12-31 13F MONOLITHIC PWR SYS COM 609839105 148,578 -4,653 -3.04 73,298 -1.31 0.0393
2021-11-10 2021-09-30 13F MONOLITHIC PWR SYS COM 609839105 153,231 31,277 25.65 74,268 63.07 0.0439
2021-08-10 2021-06-30 13F MONOLITHIC PWR SYS COM 609839105 121,954 -8,045 -6.19 45,544 -0.81 0.0274
2021-05-13 2021-03-31 13F MONOLITHIC PWR SYS COM 609839105 129,999 82,212 172.04 45,917 162.38 0.0297
2021-02-11 2020-12-31 13F MONOLITHIC PWR SYS COM 609839105 47,787 -20,390 -29.91 17,500 -8.20 0.0103
2020-11-12 2020-09-30 13F MONOLITHIC PWR SYS COM 609839105 68,177 5,853 9.39 19,064 29.07 0.0124
2020-08-12 2020-06-30 13F MONOLITHIC PWR SYS COM 609839105 62,324 35,644 133.60 14,770 230.57 0.0115
2020-05-12 2020-03-31 13F MONOLITHIC PWR SYS COM 609839105 26,680 -6,758 -20.21 4,468 -24.95 0.0040
2020-02-12 2019-12-31 13F MONOLITHIC PWR SYS COM 609839105 33,438 12,945 63.17 5,953 86.67 0.0043
2019-11-08 2019-09-30 13F MONOLITHIC PWR SYS COM 609839105 20,493 -8,806 -30.06 3,189 -19.83 0.0025
2019-08-12 2019-06-30 13F MONOLITHIC PWR SYS COM 609839105 29,299 17,252 143.21 3,978 143.75 0.0032
2019-05-13 2019-03-31 13F MONOLITHIC PWR SYS COM 609839105 12,047 -14,405 -54.46 1,632 -46.94 0.0016
2019-02-12 2018-12-31 13F MONOLITHIC PWR SYS COM 609839105 26,452 3,050 13.03 3,076 4.73 0.0031
2018-11-13 2018-09-30 13F MONOLITHIC PWR SYS COM 609839105 23,402 17,235 279.47 2,937 256.00 0.0026
2018-08-10 2018-06-30 13F MONOLITHIC PWR SYS COM 609839105 6,167 -11,051 -64.18 825 -58.61 0.0008
2018-05-11 2018-03-31 13F MONOLITHIC PWR SYS COM 609839105 17,218 12,371 255.23 1,993 265.69 0.0016
2018-02-12 2017-12-31 13F MONOLITHIC PWR SYS COM 609839105 4,847 -2,153 -30.76 545 -26.94 0.0004
2017-11-13 2017-09-30 13F MONOLITHIC PWR SYS COM 609839105 7,000 1,932 38.12 746 52.87 0.0006
2017-08-11 2017-06-30 13F MONOLITHIC PWR SYS COM 609839105 5,068 -5,698 -52.93 488 -50.81 0.0004
2017-05-12 2017-03-31 13F MONOLITHIC PWR SYS COM 609839105 10,766 -40,860 -79.15 992 -76.54 0.0009
2017-02-10 2016-12-31 13F MONOLITHIC PWR SYS COM 609839105 51,626 51,559 76,953.73 4,229 84,480.00 0.0038
2016-11-10 2016-09-30 13F MONOLITHIC PWR SYS COM 609839105 67 -18,870 -99.65 5 -99.61 0.0000
2016-08-12 2016-06-30 13F MONOLITHIC PWR SYS COM 609839105 18,937 -16,234 -46.16 1,293 -42.23 0.0013
2016-05-13 2016-03-31 13F MONOLITHIC PWR SYS COM 609839105 35,171 23,140 192.34 2,238 191.79 0.0025
2016-02-12 2015-12-31 13F MONOLITHIC PWR SYS COM 609839105 12,031 4,523 60.24 767 99.74 0.0008
2015-11-13 2015-09-30 13F MONOLITHIC PWR SYS COM 609839105 7,508 6,603 729.61 384 734.78 0.0004
2015-08-13 2015-06-30 13F MONOLITHIC PWR SYS COM 609839105 905 -3,937 -81.31 46 -81.96 0.0000
2015-05-14 2015-03-31 13F MONOLITHIC PWR SYS COM 609839105 4,842 -10,572 -68.59 255 -66.75 0.0002
2015-02-17 2014-12-31 13F MONOLITHIC PWR SYS COM 609839105 15,414 12,412 413.46 767 481.06 0.0007
2014-11-14 2014-09-30 13F MONOLITHIC PWR SYS COM 609839105 3,002 -7,033 -70.08 132 -68.94 0.0001
2014-08-14 2014-06-30 13F MONOLITHIC PWR SYS COM 609839105 10,035 1,207 13.67 425 23.91 0.0004
2014-05-15 2014-03-31 13F MONOLITHIC PWR SYS COM 609839105 8,828 -3,660 -29.31 343 -20.79 0.0004
2014-02-14 2013-12-31 13F MONOLITHIC PWR SYS COM 609839105 12,488 12,300 6,542.55 433 7,116.67 0.0004
2013-11-14 2013-09-30 13F MONOLITHIC PWR SYS COM 609839105 188 -23 -10.90 6 20.00 0.0000
2013-08-14 2013-06-30 13F MONOLITHIC PWR SYS COM 609839105 211 211 5 0.0000
Disclosed Call Options
File
Date
Effective
Date
Form Security Class ID Opt Avg Share
Price
Shares ΔShares
(%)
Value
(x1000)
ΔValue
(%)
Prior Allocation
(%)
Allocation
(%)
ΔAllocation
(%)
Cost Basis
(x1000)
Profit
(x1000)
Return
(%)
2019-02-12 2018-12-31 13F MONOLITHIC PWR SYS COM Call 0 -100.00 0 -100.00 n/a n/a n/a
2018-11-13 2018-09-30 13F MONOLITHIC PWR SYS COM Call 24,500 3,075 n/a n/a n/a
Disclosed Put Options
File
Date
Effective
Date
Form Security Class ID Opt Avg Share Price Shares ΔShares
(%)
Value
(x1000)
ΔValue
(%)
Prior Allocation
(%)
Allocation
(%)
ΔAllocation
(%)
Cost Basis
(x1000)
Profit
(x1000)
Return
(%)
2019-02-12 2018-12-31 13F MONOLITHIC PWR SYS COM Put 0 -100.00 0 -100.00 n/a n/a n/a
2018-11-13 2018-09-30 13F MONOLITHIC PWR SYS COM Put 24,500 3,075 n/a n/a n/a
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.