![]() that's not a problem when dealing with standard transistors. If you are using anything in a T0-220 package to drive a relay. If it's a 2N7000 NCHANNEL MOSFET or 2N2222 NPN transistor you are going to spend about $0.50 for either one, on average. Digging even deeper into transistor types, there are actually two versions of the BJT: NPN and PNP. In this tutorial we'll focus on the BJT, because it's slightly easier to understand. A 2N2222A can cope with up to 800ma and you usually only need to add a 1K resistor at the base. There are two types of basic transistor out there: bi-polar junction (BJT) and metal-oxide field-effect (MOSFET). which is why many draw less than 100 ma and most are between 100-300ma. (you need a extra level converter transistor too) but the relay is supposed to SAVE you from doing the heavy lifting. and the relay draws more than the average hundred or so milliamps. ![]() where you really are driving the relay with 12 volts. or because they thought it was just BETTER to use one and it ends up being a complete waste of (or lack of) engineering if used to drive a 5V relay in a 5 Volt circuit. because they thought a MOSFET is a MOSFET. How often have we seen people misuse/misapply the IRF510. Literally interchangeable and 2N2222 might even be superior. Read the WIKI on the 2N7000 mosfet and then read the 2N2222. geez the 2N2222 IS BARELY working hard to drive a simple relay like that. Unless you are trying to drive a relay yanked out of an Automobile whose coil might draw hundreds of milliamps, your average 2N2222 transistor will easily drive a small relay. I feel strongly that bipolar transistors are easier for newcomers to electronics to deal with. What is required for direct connection from output pins is a LOGIC level mosfetĪgain both bipolar transistors and mosfet transistors can operate as digital switching or linear amplification devices, it all depends on the base biasing condition or source/gate voltage bias applied.Įach has it's place. Note that most mosfets won't fully turn on at the Arduino 5volt logic level output pins, as typically they require a +10 volt gate voltage for minimum source/drain resistance. ![]() Yes MOSFETs (with suitable ratings) are very good for high current switching application, if the appropriate gate voltage is applied. To energize a relay, where the load is fully ON, or fully OFF all the time, either would work ok, but a MOSFET is best due to low voltage drop across MOSFET and not requiring as much heat sink. A mosfet can be used as a linear device as well as a switching device, again it's all in how much bias voltage is applied to the source/gate. A mosfet can also be used in a bypass application, it's all in how much gate voltage you apply. That is why a bipolar transistor can be used as bypass transistor in a regulated power supply - i.e.
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