Monolithic Power Systems, Inc.
US ˙ NasdaqGS ˙ US6098391054

SecurityMPWR / Monolithic Power Systems, Inc.
InstitutionWhittier Trust Co
Latest Disclosed Ownership42,010 shares
Latest Disclosed Value $ 49,573,061
Whittier Trust Co reports 5.07% decrease in ownership of MPWR / Monolithic Power Systems, Inc.

On April 28, 2026 - Whittier Trust Co filed a 13F-HR form disclosing ownership of 42,010 shares of Monolithic Power Systems, Inc. (US:MPWR) valued at $45,931,633 USD as of March 31, 2026. The entity filed a previous 13F-HR on January 26, 2026 disclosing 44,252 shares of Monolithic Power Systems, Inc.. This represents a change in shares of -5.07% during the quarter. The current value of the position is $70,992,279 USD.

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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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)
2026-04-28 2026-03-31 13F MONOLITHIC common 609839105 42,010 -2,242 -5.07 49,573 11.43 0.5594
2026-01-26 2025-12-31 13F MONOLITHIC common 609839105 44,252 51 0.12 44,490 9.55 0.4818
2025-10-31 2025-09-30 13F MONOLITHIC PWR SYS common 609839105 44,201 678 1.56 40,613 27.59 0.4623
2025-07-30 2025-06-30 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 43,523 1,037 2.44 31,832 29.18 0.3838
2025-05-02 2025-03-31 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 42,486 954 2.30 24,640 0.27 0.3433
2025-02-11 2024-12-31 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 41,532 1,242 3.08 24,574 -34.03 0.3238
2024-10-21 2024-09-30 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 40,290 1,406 3.62 37,248 16.59 0.4985
2024-07-29 2024-06-30 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 38,884 1,793 4.83 31,950 27.16 0.4533
2024-05-02 2024-03-31 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 37,091 1,271 3.55 25,126 11.20 0.3663
2024-01-11 2023-12-31 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 35,820 -2,967 -7.65 22,594 26.09 0.3663
2023-10-27 2023-09-30 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 38,787 846 2.23 17,920 -12.57 0.3185
2023-07-24 2023-06-30 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 37,941 -4,658 -10.93 20,496 -3.87 0.3563
2023-04-21 2023-03-31 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 42,599 3,507 8.97 21,322 54.25 0.3882
2023-01-25 2022-12-31 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 39,092 -9,609 -19.73 13,823 -21.90 0.2689
2022-10-21 2022-09-30 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 48,701 1,991 4.26 17,697 -1.34 0.3709
2022-07-28 2022-06-30 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 46,710 506 1.10 17,937 -20.07 0.3623
2022-04-29 2022-03-31 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 46,204 1,881 4.24 22,440 2.63 0.3784
2022-01-19 2021-12-31 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 44,323 -5,084 -10.29 21,866 -8.69 0.3553
2021-11-01 2021-09-30 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 49,407 -525 -1.05 23,946 28.42 0.4360
2021-07-29 2021-06-30 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 49,932 2,806 5.95 18,647 12.03 0.3322
2021-04-26 2021-03-31 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 47,126 3,243 7.39 16,645 3.57 0.3233
2021-01-29 2020-12-31 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 43,883 -13,500 -23.53 16,071 0.16 0.3433
2020-10-30 2020-09-30 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 57,383 519 0.91 16,045 19.05 0.3820
2020-07-10 2020-06-30 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 56,864 -885 -1.53 13,477 39.35 0.3743
2020-04-27 2020-03-31 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 57,749 2,931 5.35 9,671 -0.90 0.3158
2020-01-31 2019-12-31 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 54,818 1,269 2.37 9,759 17.10 0.2560
2019-10-18 2019-09-30 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 53,549 561 1.06 8,334 15.83 0.2385
2019-07-23 2019-06-30 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 52,988 2,198 4.33 7,195 4.55 0.2113
2019-04-29 2019-03-31 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 50,790 2,627 5.45 6,882 22.91 0.2104
2019-02-07 2018-12-31 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 48,163 2,684 5.90 5,599 -1.93 0.1926
2018-10-23 2018-09-30 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 45,479 187 0.41 5,709 -5.71 0.1781
2018-07-27 2018-06-30 13F/A-1 MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 45,292 2,690 6.31 6,055 22.77 0.2000
2018-07-20 2018-06-30 13F MONOLITHIC PWR SYS INC COM US SMALL AND MID-CAP EQUITIES 609839105 43,530 928 1,843
2018-05-01 2018-03-31 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 42,602 583 1.39 4,932 4.47 0.1657
2018-02-07 2017-12-31 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 42,019 757 1.83 4,721 7.39 0.1647
2017-10-23 2017-09-30 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 41,262 584 1.44 4,396 12.11 0.1602
2017-07-20 2017-06-30 13F MONOLITHIC PWR SYS INC COM US SMALL-CAP EQUITIES 609839105 40,678 1,132 2.86 3,921 7.66 0.1516
2017-04-26 2017-03-31 13F MONOLITHIC PWR SYS US SMALL AND MID-CAP EQUITIES 609839105 39,546 1,800 4.77 3,642 17.75 0.1469
2017-01-18 2016-12-31 13F MONOLITHIC PWR SYS INC COM US SMALL AND MID-CAP EQUITIES 609839105 37,746 208 0.55 3,093 2.35 0.1316
2016-11-10 2016-09-30 13F MONOLITHIC PWR SYS INC COM US SMALL AND MID-CAP EQUITIES 609839105 37,538 77 0.21 3,022 18.09 0.1316
2016-07-28 2016-06-30 13F MONOLITHIC PWR SYS INC COM US SMALL AND MID-CAP EQUITIES 609839105 37,461 453 1.22 2,559 8.66 0.1127
2016-04-28 2016-03-31 13F MONOLITHIC PWR SYS INC COM US SMALL AND MID-CAP EQUITIES 609839105 37,008 0 0.00 2,355 -0.08 0.1041
2016-02-10 2015-12-31 13F MONOLITHIC PWR SYS INC COM US SMALL AND MID-CAP EQUITIES 609839105 37,008 -6,522 -14.98 2,357 5.74 0.1070
2015-11-12 2015-09-30 13F MONOLITHIC PWR SYS INC COM US SMALL AND MID-CAP EQUITIES 609839105 43,530 0 0.00 2,229 1.00 0.1084
2015-08-13 2015-06-30 13F MONOLITHIC PWR SYS INC COM US SMALL AND MID-CAP EQUITIES 609839105 43,530 0 0.00 2,207 -3.71 0.0980
2015-05-05 2015-03-31 13F MONOLITHIC PWR SYS INC COM US SMALL AND MID-CAP EQUITIES 609839105 43,530 43,530 0.00 2,292 0.1051
2015-02-04 2014-12-31 13F MONOLITHIC PWR SYS INC COM US SMALL AND MID-CAP EQUITIES 609839105 0 -43,530 -100.00 0 -100.00
2014-11-07 2014-09-30 13F MONOLITHIC PWR SYS INC COM US SMALL AND MID-CAP EQUITIES 609839105 43,530 0 0.00 1,917 4.02 0.0934
2014-08-04 2014-06-30 13F MONOLITHIC PWR SYS INC COM US SMALL AND MID-CAP EQUITIES 609839105 43,530 0 0.00 1,843 9.18 0.0909
2014-05-01 2014-03-31 13F MONOLITHIC PWR SYS INC COM US SMALL AND MID-CAP EQUITIES 609839105 43,530 0 0.00 1,688 11.94 0.0865
2014-02-05 2013-12-31 13F MONOLITHIC PWR SYS INC COM US SMALL AND MID-CAP EQUITIES 609839105 43,530 0 0.00 1,508 14.42 0.0773
2013-11-18 2013-09-30 13F MONOLITHIC PWR SYS COM 609839105 43,530 0 0.00 1,318 25.52 0.0713
2013-08-14 2013-06-30 13F MONOLITHIC PWR SYS COM 609839105 43,530 43,530 1,050 0.0588
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.