![]() Such transistors are commonly found in products such as hearing aids, radio, or anything from the µV range. Transistors as AmplifierĪpart from working as switches, transistors work as an amplifier as well, taking tiny electric currents, and producing a much higher current output at the other end. Transistors as switches can be seen in memory chips, where there are millions of transistors present, switching on and off. In other words, a small current flowing through one part of a transistor allows for a much bigger current flow through another part of the transistor. Such an application is used to control the flow of power to another part of a circuit. Switches turn on and off, where for transistors, it acts as such by creating a binary on/off effect of a switch, hence not requiring an actuator for it to flip, but instead voltages. For common electrical circuit usages or low current in-home applications, BJTs may well be sufficient in handling the jobĪ transistor is most commonly used as either electronic switches in digital circuits or as an amplifier.If you’re looking to regulate the flow of high current in narrow pulses, or for any high power applications, MOSFET is the way to go.Here’s what each transistor are suitable for: Metal oxide semiconductor field-effect transistorģ terminals: Gate, source, drain with higher structure complexityįor MOSFET to work, it’s dependent on the voltage at the oxide insulated gate electrodeįor BJTs to work, it’s dependent on the current at the base terminalĪlthough MOSFET holds advantages over BJT such as voltage control, choosing either comes down to your application purposes. Now that we’ve covered both types of transistors BJT and FET (Commonly known MOSFET), let’s take a look at their differences shown in the table below: The wider the channel region, the better conductivity of a device will be. When voltage is applied at the gate, it generates an electrical field that changes the width of the channel region, where the electrons flow. A DC circuit is then formed by connecting a voltage source between these two n-type regions (marked in red).The gate terminal is then brought out from the thin metallic plate.A thin insulated metallic plate is then placed on top of the silicon dioxide, acting as a capacitor plate.The entire surface of the substrate is coated with a layer of silicon dioxide.The drain terminals (Source and Drain) are then brought out from these two end regions.Two sides on this p-type substrate are made highly doped with an n-type impurity (marked as n+).A block, also known as a substrate of p-type semiconductor acts as the base for MOSFET.To understand how FET work, we’ll take a look at a typical circuit diagram as follows: MOSFET Diagram With its different pin construction, it works slightly differently as compared to BJTs. What is FET and How does it work?įield-Effect Transistor, the other type of transistor, is most commonly classified as MOSFET (metal-oxide-semiconductor field-effect transistor) and is constructed with pins Gate, source, drain. Additionally, instead of emitting electrons, the emitter in a PNP emits “holes” (a conceptual absence of electrons), which are then collected by the collector. Essentially, current flow is still controlled by the base but flows in the opposite direction. Whereas for a PNP transistor, it consists of a layer of N-doped semiconductor between two layers of P-doped material, where the base current entering into the collector is amplified. The emitted electrons are finally collected by the collector and sent to the following part of a circuit. The emitter then “emits” electrons into the base, with the base controlling the no. Now that we’ve defined what are BJTs, we’ll take a look at how BJTs work with a simple illustration below: Refįor an NPN transistor, it consists of a layer of P-doped semiconductor between two layers of N-doped material, where electrons are passed from the emitter to the collector instead. ![]() The difference between the two can be spotted with the arrow direction where for NPN, the arrow’s exiting the base while for PNP, the arrow’s entering the base. ![]() Firstly, for BJTs, it comes in two iterations or versions NPN and PNP BJT, with its circuit symbols as shown below: BJTs: NPN vs PNP circuit symbolsĪs you can see, both NPN and PNP iterations have pins labeled Collector (C), Base (B), and emitter (E).
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