Working with Transistor

In today’s lecture, we learned the new device named transistor which is act like an ON/OFF switch. The transistor can be made of either “N-P-N” or “P-N-P” form. It has three legs, a gate (connected to ground), a collector (high potential), and an emitter (low potential). When a small current flow into the gate as key opens the door, main current can get through from the collector to emitter, increasing as linear function. However, the main current will maintain same value if the gate current reaches some certain value. After learned the properties of transistor, we designed a circuit controlled by it. A LED and a fan were turned on/off in some time intervals determined by program. The advantage of using the transistor is: we can design a circuit with two power supplies, one for “brain” (run by a small battery) and one for body (mechanical part, run by large battery), to avoid wasting power.