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MPS Monolithic Power Systems Announces Results for the First Quarter Ended March 31 , 2021 ● Exhibit 99.1 PRESS RELEASE For Immediate Release KIRKLAND , WASHINGTON , May 4 , 2021- Monolithic Power Systems , Inc. ( MPS ) ( Nasdaq : MPWR ) , a leading company in high performance analog solutions , today announced financial results for the quarter ended March 31 , 2021 . ● Revenue was $ 254.5 million for the quarter ended March 31 , 2021 , a 9.2 % increase from $ 233.0 million for the quarter ended December 31 , 2020 and a 53.5 % increase from $ 165.8 million for the quarter ended March 31 , 2020 . GAAP gross margin was 55.4 % for the quarter ended March 31 , 2021 , compared with 55.2 % for the quarter ended March 31 , 2020 . Non - GAAP ( 1 ) gross margin was 55.8 % for the quarter ended March 31 , 2021 , excluding the impact of $ 0.8 million for stock - based compensation expense and $ 0.2 million for deferred compensation plan expense , compared with 55.5 % for the quarter ended March 31 , 2020 , excluding the impact of $ 0.6 million for stock - based compensation expense and $ 0.1 million for deferred compensation plan income . GAAP operating expenses were $ 95.0 million for the quarter ended March 31 , 2021 , compared with $ 60.5 million for the quarter ended March 31 , 2020 . Non - GAAP ( 1 ) operating expenses were $ 66.2 million for the quarter ended March 31 , 2021 , excluding $ 27.8 million for stock - based compensation expense and $ 1.0 million for deferred compensation plan expense , compared with $ 46.1 million for the quarter ended March 31 , 2020 , excluding $ 18.0 million for stock - based compensation expense and $ 3.6 million for deferred compensation plan income . ● GAAP operating income was $ 46.1 million for the quarter ended March 31 , 2021 , compared with $ 31.0 million for the quarter ended March 31 , 2020 . Non - GAAP ( 1 ) operating income was $ 75.8 million for the quarter ended March 31 , 2021 , excluding $ 28.6 million for stock - based compensation expense and $ 1.1 million for deferred compensation plan expense , compared with $ 45.9 million for the quarter ended March 31 , 2020 , excluding $ 18.6 million for stock - based compensation expense and $ 3.7 million for deferred compensation plan income . GAAP other income , net , was $ 2.6 million for the quarter ended March 31 , 2021 , compared with other expense , net , of $ 1.7 million for the quarter ended March 31 , 2020 . Non - GAAP ( 1 ) other income , net , was $ 1.4 million for the quarter ended March 31 , 2021 , excluding $ 1.2 million for deferred compensation plan income , compared with other income , net , of $ 2.0 million for the quarter ended March 31 , 2020 , excluding $ 3.8 million for deferred compensation plan expense . ● GAAP income before income taxes was $ 48.7 million for the quarter ended March 31 , 2021 , compared with $ 29.3 million for the quarter ended March 31 , 2020 . Non - GAAP ( 1 ) income before income taxes was $ 77.2 million for the quarter ended March 31 , 2021 , excluding $ 28.6 million for stock - based compensation expense and $ 0.1 million for deferred compensation plan income , compared with $ 47.9 million for the quarter ended March 31 , 2020 , excluding $ 18.6 million for stock - based compensation expense , and $ 0.1 million for deferred compensation plan expense .