Recently, i am going to start my new projects about calibration circuits. Before thisI was just wondering about calibration circuits for phototransistors to account for degradation of the LED or photo, transistor ? Is that necessary , do they degrade quickly ? I read the Tutorial for Phototransistor(reference: https://www.kynix.com/Blog/The-Best-Tutorial-for-Phototransistor.html) but i am still confused.