A closer look to the factors affecting the switching transient times of optocouplers

The significant parameters for a high-speed optoelectronic switch were the transient times. In the time domain, there is a time elapsed on the order of microseconds between applying a current pulse and seeing an output. Therefore, the present work aimed to give a closer look on the factors affecting the transient times of the optocoupler switching action, namely; delay (t_d)-, rise (t_r)-, in addition to storage (t_s)- and fall (t_f)-times. The turn-on time (T_on = t_d + t_r) and turn-off time (T_off = t_s + t_f) of the optocoupler (type 4N25) were investigated and plotted under the influence of different operating conditions such as: load resistance (R_L), forward LED drive current (I_F), bias collector voltage (V_CC), emitter–base resistance (R_BE), and ambient temperature.