Monolithic Power Systems, Inc.
US ˙ NasdaqGS ˙ US6098391054

SecurityMPWR / Monolithic Power Systems, Inc.
InstitutionJane Street Group, Llc
Latest Disclosed Ownership5,083 shares
Latest Disclosed Value $ 5,557,498
Jane Street Group, Llc ownership in MPWR / Monolithic Power Systems, Inc.

On May 12, 2026 - Jane Street Group, Llc filed a 13F-HR form disclosing ownership of 5,083 shares of Monolithic Power Systems, Inc. (US:MPWR) valued at $5,557,498 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 12, 2026 disclosing 4,487 shares of Monolithic Power Systems, Inc.. This represents a change in shares of 13.28% during the quarter. The current value of the position is $7,528,177 USD.

Jane Street Group, Llc 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 19,200 of underlying shares valued at $20,992,320 USD and put options representing 47,600 of underlying shares valued at $52,043,460 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.

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)
2026-05-12 2026-03-31 13F MONOLITHIC PWR SYS COM 609839105 5,083 596 13.28 5,557 36.67 0.0007
2026-02-12 2025-12-31 13F MONOLITHIC PWR SYS COM 609839105 4,487 -9,901 -68.81 4,067 -69.30 0.0006
2025-11-14 2025-09-30 13F MONOLITHIC PWR SYS COM 609839105 14,388 9,316 183.68 13,246 257.13 0.0020
2025-08-14 2025-06-30 13F MONOLITHIC PWR SYS COM 609839105 5,072 4,050 396.28 3,710 526.52 0.0007
2025-05-19 2025-03-31 13F/A-1 MONOLITHIC PWR SYS COM 609839105 1,022 -15,078 -93.65 593 -93.79 0.0001
2025-05-14 2025-03-31 13F MONOLITHIC PWR SYS COM 609839105 1,022 -15,078 593 0.0001
2025-02-14 2024-12-31 13F MONOLITHIC PWR SYS COM 609839105 16,100 -117,560 -87.95 9,526 -92.29 0.0021
2024-11-15 2024-09-30 13F MONOLITHIC PWR SYS COM 609839105 133,660 88,901 198.62 123,569 235.99 0.0273
2024-08-15 2024-06-30 13F MONOLITHIC PWR SYS COM 609839105 44,759 23,679 112.33 36,778 157.54 0.0084
2024-05-16 2024-03-31 13F MONOLITHIC PWR SYS COM 609839105 21,080 -39,244 -65.06 14,280 -62.47 0.0030
2024-02-15 2023-12-31 13F MONOLITHIC PWR SYS COM 609839105 60,324 52,868 709.07 38,051 1,004.85 0.0099
2023-11-15 2023-09-30 13F MONOLITHIC PWR SYS COM 609839105 7,456 -14,836 -66.55 3,445 -71.40 0.0011
2023-08-14 2023-06-30 13F MONOLITHIC PWR SYS COM 609839105 22,292 -11,682 -34.39 12,043 -29.19 0.0041
2023-05-16 2023-03-31 13F MONOLITHIC PWR SYS COM 609839105 33,974 26,598 360.60 17,005 552.03 0.0070
2023-02-15 2022-12-31 13F MONOLITHIC PWR SYS COM 609839105 7,376 -14,999 -67.03 2,608 -67.93 0.0012
2022-11-15 2022-09-30 13F MONOLITHIC PWR SYS COM 609839105 22,375 13,538 153.20 8,131 139.57 0.0036
2022-08-16 2022-06-30 13F MONOLITHIC PWR SYS COM 609839105 8,837 5,474 162.77 3,394 107.84 0.0014
2022-05-17 2022-03-31 13F MONOLITHIC PWR SYS COM 609839105 3,363 -2,997 -47.12 1,633 -47.96 0.0005
2022-02-15 2021-12-31 13F MONOLITHIC PWR SYS COM 609839105 6,360 1,753 38.05 3,138 40.53 0.0010
2021-11-16 2021-09-30 13F MONOLITHIC PWR SYS COM 609839105 4,607 4,607 2,233 0.0008
2021-08-16 2021-06-30 13F MONOLITHIC PWR SYS COM 609839105 0 -4,236 -100.00 0 -100.00
2021-05-18 2021-03-31 13F MONOLITHIC PWR SYS COM 609839105 4,236 2,831 201.49 1,496 191.05 0.0007
2021-02-17 2020-12-31 13F MONOLITHIC PWR SYS COM 609839105 1,405 -29,283 -95.42 514 -94.01 0.0003
2020-11-17 2020-09-30 13F MONOLITHIC PWR SYS COM 609839105 30,688 30,688 8,580 0.0052
2020-08-17 2020-06-30 13F MONOLITHIC PWR SYS COM 609839105 0 -3,657 -100.00 0 -100.00
2020-05-15 2020-03-31 13F MONOLITHIC PWR SYS COM 609839105 3,657 1,461 66.53 612 56.52 0.0006
2020-02-14 2019-12-31 13F MONOLITHIC PWR SYS COM 609839105 2,196 -119 -5.14 391 8.61 0.0005
2019-11-14 2019-09-30 13F MONOLITHIC PWR SYS COM 609839105 2,315 564 32.21 360 51.26 0.0006
2019-08-15 2019-06-30 13F MONOLITHIC PWR SYS COM 609839105 1,751 -5,771 -76.72 238 -76.64 0.0004
2019-05-16 2019-03-31 13F MONOLITHIC PWR SYS COM 609839105 7,522 7,522 1,019 0.0017
2019-02-14 2018-12-31 13F MONOLITHIC PWR SYS COM 609839105 0 -8,339 -100.00 0 -100.00
2018-11-14 2018-09-30 13F MONOLITHIC PWR SYS COM 609839105 8,339 -27,412 -76.67 1,047 -78.09 0.0021
2018-08-15 2018-06-30 13F MONOLITHIC PWR SYS COM 609839105 35,751 35,751 4,779 0.0112
2018-05-15 2018-03-31 13F MONOLITHIC PWR SYS COM 609839105 0 -4,532 -100.00 0 -100.00
2018-02-15 2017-12-31 13F MONOLITHIC PWR SYS COM 609839105 4,532 -4,092 -47.45 509 -44.61 0.0015
2017-11-14 2017-09-30 13F MONOLITHIC PWR SYS COM 609839105 8,624 2,044 31.06 919 51.65 0.0030
2017-05-15 2017-03-31 13F MONOLITHIC PWR SYS COM 609839105 6,580 6,580 606 0.0027
2016-05-17 2016-03-31 13F MONOLITHIC PWR SYS COM 609839105 0 -8,162 -100.00 0 -100.00
2016-02-16 2015-12-31 13F MONOLITHIC PWR SYS COM 609839105 8,162 8,162 520 0.0032
2015-11-16 2015-09-30 13F MONOLITHIC PWR SYS COM 609839105 0 -4,541 -100.00 0 -100.00
2015-08-14 2015-06-30 13F MONOLITHIC PWR SYS COM 609839105 4,541 4,541 230 0.0015
2015-02-17 2014-12-31 13F MONOLITHIC PWR SYS COM 609839105 0 -10,324 -100.00 0 -100.00
2014-11-14 2014-09-30 13F MONOLITHIC PWR SYS COM 609839105 10,324 10,324 455 0.0046
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
(%)
2026-05-12 2026-03-31 13F MONOLITHIC PWR SYS COM Call 19,200 -23.81 20,992 -8.09 n/a n/a n/a
2026-02-12 2025-12-31 13F MONOLITHIC PWR SYS COM Call 25,200 10.53 22,840 8.81 n/a n/a n/a
2025-11-14 2025-09-30 13F MONOLITHIC PWR SYS COM Call 22,800 48.05 20,991 86.36 n/a n/a n/a
2025-08-14 2025-06-30 13F MONOLITHIC PWR SYS COM Call 15,400 -15.85 11,263 6.12 n/a n/a n/a
2025-05-19 2025-03-31 13F/A MONOLITHIC PWR SYS COM Call 18,300 -72.89 10,614 -73.43 n/a n/a n/a
2025-05-14 2025-03-31 13F MONOLITHIC PWR SYS COM Call 18,300 10,614 n/a n/a n/a
2025-02-14 2024-12-31 13F MONOLITHIC PWR SYS COM Call 67,500 375.35 39,940 204.25 n/a n/a n/a
2024-11-15 2024-09-30 13F MONOLITHIC PWR SYS COM Call 14,200 -36.61 13,128 -28.68 n/a n/a n/a
2024-08-15 2024-06-30 13F MONOLITHIC PWR SYS COM Call 22,400 -49.09 18,406 -38.25 n/a n/a n/a
2024-05-16 2024-03-31 13F MONOLITHIC PWR SYS COM Call 44,000 -34.33 29,806 -29.47 n/a n/a n/a
2024-02-15 2023-12-31 13F MONOLITHIC PWR SYS COM Call 67,000 30.60 42,262 78.32 n/a n/a n/a
2023-11-15 2023-09-30 13F MONOLITHIC PWR SYS COM Call 51,300 905.88 23,701 760.25 n/a n/a n/a
2023-08-14 2023-06-30 13F MONOLITHIC PWR SYS COM Call 5,100 -51.43 2,755 -47.57 n/a n/a n/a
2023-05-16 2023-03-31 13F MONOLITHIC PWR SYS COM Call 10,500 -30.00 5,256 -0.92 n/a n/a n/a
2023-02-15 2022-12-31 13F MONOLITHIC PWR SYS COM Call 15,000 -40.94 5,304 -42.54 n/a n/a n/a
2022-11-15 2022-09-30 13F MONOLITHIC PWR SYS COM Call 25,400 45.98 9,230 38.13 n/a n/a n/a
2022-08-16 2022-06-30 13F MONOLITHIC PWR SYS COM Call 17,400 -75.83 6,682 -80.89 n/a n/a n/a
2022-05-17 2022-03-31 13F MONOLITHIC PWR SYS COM Call 72,000 9.09 34,969 7.40 n/a n/a n/a
2022-02-15 2021-12-31 13F MONOLITHIC PWR SYS COM Call 66,000 -18.32 32,560 -16.86 n/a n/a n/a
2021-11-16 2021-09-30 13F MONOLITHIC PWR SYS COM Call 80,800 608.77 39,162 819.94 n/a n/a n/a
2021-08-16 2021-06-30 13F MONOLITHIC PWR SYS COM Call 11,400 9.62 4,257 15.90 n/a n/a n/a
2021-05-18 2021-03-31 13F MONOLITHIC PWR SYS COM Call 10,400 48.57 3,673 43.25 n/a n/a n/a
2021-02-17 2020-12-31 13F MONOLITHIC PWR SYS COM Call 7,000 -60.23 2,564 -47.90 n/a n/a n/a
2020-11-17 2020-09-30 13F MONOLITHIC PWR SYS COM Call 17,600 104.65 4,921 141.46 n/a n/a n/a
2020-08-17 2020-06-30 13F MONOLITHIC PWR SYS COM Call 8,600 2,038 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
(%)
2026-05-12 2026-03-31 13F MONOLITHIC PWR SYS COM Put 47,600 10.19 52,043 32.92 n/a n/a n/a
2026-02-12 2025-12-31 13F MONOLITHIC PWR SYS COM Put 43,200 45.45 39,155 43.20 n/a n/a n/a
2025-11-14 2025-09-30 13F MONOLITHIC PWR SYS COM Put 29,700 -0.67 27,343 25.04 n/a n/a n/a
2025-08-14 2025-06-30 13F MONOLITHIC PWR SYS COM Put 29,900 28.88 21,868 62.53 n/a n/a n/a
2025-05-19 2025-03-31 13F/A MONOLITHIC PWR SYS COM Put 23,200 -69.83 13,456 -70.43 n/a n/a n/a
2025-05-14 2025-03-31 13F MONOLITHIC PWR SYS COM Put 23,200 13,456 n/a n/a n/a
2025-02-14 2024-12-31 13F MONOLITHIC PWR SYS COM Put 76,900 96.17 45,502 25.55 n/a n/a n/a
2024-11-15 2024-09-30 13F MONOLITHIC PWR SYS COM Put 39,200 -22.22 36,240 -12.49 n/a n/a n/a
2024-08-15 2024-06-30 13F MONOLITHIC PWR SYS COM Put 50,400 -25.22 41,413 -9.30 n/a n/a n/a
2024-05-16 2024-03-31 13F MONOLITHIC PWR SYS COM Put 67,400 15.81 45,658 24.37 n/a n/a n/a
2024-02-15 2023-12-31 13F MONOLITHIC PWR SYS COM Put 58,200 31.67 36,711 79.78 n/a n/a n/a
2023-11-15 2023-09-30 13F MONOLITHIC PWR SYS COM Put 44,200 978.05 20,420 822.31 n/a n/a n/a
2023-08-14 2023-06-30 13F MONOLITHIC PWR SYS COM Put 4,100 -6.82 2,215 0.54 n/a n/a n/a
2023-05-16 2023-03-31 13F MONOLITHIC PWR SYS COM Put 4,400 -53.68 2,202 -34.44 n/a n/a n/a
2023-02-15 2022-12-31 13F MONOLITHIC PWR SYS COM Put 9,500 -62.60 3,359 -63.61 n/a n/a n/a
2022-11-15 2022-09-30 13F MONOLITHIC PWR SYS COM Put 25,400 22.12 9,230 15.55 n/a n/a n/a
2022-08-16 2022-06-30 13F MONOLITHIC PWR SYS COM Put 20,800 -42.38 7,988 -54.44 n/a n/a n/a
2022-05-17 2022-03-31 13F MONOLITHIC PWR SYS COM Put 36,100 522.41 17,533 512.83 n/a n/a n/a
2022-02-15 2021-12-31 13F MONOLITHIC PWR SYS COM Put 5,800 -65.68 2,861 -65.07 n/a n/a n/a
2021-11-16 2021-09-30 13F MONOLITHIC PWR SYS COM Put 16,900 53.64 8,191 99.39 n/a n/a n/a
2021-08-16 2021-06-30 13F MONOLITHIC PWR SYS COM Put 11,000 -59.26 4,108 -56.93 n/a n/a n/a
2021-05-18 2021-03-31 13F MONOLITHIC PWR SYS COM Put 27,000 486.96 9,537 465.99 n/a n/a n/a
2021-02-17 2020-12-31 13F MONOLITHIC PWR SYS COM Put 4,600 -68.92 1,685 -59.28 n/a n/a n/a
2020-11-17 2020-09-30 13F MONOLITHIC PWR SYS COM Put 14,800 4,138 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.