“Can we control the conductivity of a circuit with Voltage?”
When working with electrical systems, sometimes we may want the conductivity of an element to change for different applications. However, how can we do that without doing too much work? Well, let’s use our engineering mindset to think of a solution. First, let’s build a semiconductor with two n-type depletion layers that are disconnected from each other by a p-type substrate. Then let’s position a metallic “gate” near to the two n-type inversion layers. Finally, let’s put a current source to one and a drain to the other. When we apply an electrical voltage to the gate, negative particles from the positive substrate will be pulled in its direction and p-type pushed out. This will create a bridge between the two n-type regions, and allow current to pass through. The more voltage applied, the more current can be passed. If no voltage is applied, then no current can pass! This device is known as a metal-oxide-semiconductor-field-effect transistor, or MOSFET for short. MOSFETs are some of the most used components in electronics and can be found everywhere from microcontrollers to voltage amplifiers.