Ma Photodiodes, omwe amadziwikanso kuti ma photocell, ndi zida zamagetsi zomwe zimasinthira kuwala kukhala magetsi.Amagwiritsidwa ntchito pazinthu zosiyanasiyana kuphatikiza zowonera kuwala, ma switch optical, ndi kujambula kwa digito.Ma Photodiodes amakhala ndi mphambano ya semiconductor yomwe imatulutsa ma elekitironi ikayatsidwa ndi kuwala.Mphamvu yomwe amapanga imayenderana ndi mphamvu ya kuwala, ndipo ingagwiritsidwe ntchito kuzindikira kukhalapo kwa kuwala kapena kuyesa mphamvu yake.