NMC--BJT FET Relay Comparison

Examples of how to use an NPN bipolar junction transistor (BJT, top circuit) and an N-channel field-effect transistor (FET, middle circuit) as a switch in much the same way that relays are used. Each switch circuit uses a 5 volt DC power source to turn on a 60 DC volt lamp. For comparison, the relay circuit on the bottom performs the same function. Advantages of BJT and FET vs relay: 1. Uses less power than the relay coil 2. Smaller than relays 3. Solid state...no moving parts 4. No voltage spike from relay coil Advantages of FET: 1. Uses less power than BJT 2. Controls larger load currents than BJT Advantages of a relay: 1. Can control larger loads, including AC 2. Not sensitive to static damage 3. Can use DPDT switching

published 6 years ago