![]() This can be ideal when making high input impedance buffer amplifiers. ![]() Small signal MOSFETs like the ZVN2110A and its complement, ZVP2110A can have advantages over BJT transistors in that they do not require current to turn them on, only voltage on the gate. (You sometimes see the same package used for linear regulators.) If you want to drive that much current, don’t forget to use a heat sink. The TIP31 can handle as much as 5A when in a relatively large TO-220 package. When configured as a “darlington pair” with a 2N3904 or 2N3906, they can provide significantly higher current capability than single transistors. The beta of the NPN TIP31 and PNP TIP32 can be a low as 25 which might not be high enough when driving heavy load currents. One of the advantages of BJTs is that they are easily driven from a CMOS logic I/O pin. Since a 2N3904 was included for the NPN, its complement: the 2N3906 is included. A high-side switch is where the emitter is connected to a positive voltage supply and the load is placed between the collector and ground. The current is rated at 200mA which is enough for many small DC motors, relay coils or LEDs.įor high-side switch circuits, you need a PNP type transistor. You can easily switch big 12 or 16V loads with this 40V transistor. This means whatever you want to control is connected between the high voltage and the collector of the transistor, with the emitter connected to ground as shown in the LED driver example shown in figure 1.Ī common NPN transistor is the 2N3904. NPN Transistors are used in low-side switch circuits. Commonly found as through-hole parts in the 3-pin TO-92 style package. These are the workhorses of most control circuits, for low current applications. With Vbe around 0.7 volts, the base can be driven with a high value resistor directly from CMOS I/O pins and they are generally rather low cost. Here are some more details on each of the ones on our list.īipolar transistors come in small packages. For NPN look at the BC547 or 2SC1815, for PNP the BC557 or 2SA1015. There are European and Japanese equivalents that may be more available if you are located in that part of the world. This can often be accomplished with either a BJT or MOSFET, depending on the load current and voltage you need to switch. For many projects, they are used to switch on and off a load that requires current much larger than the I/O pin of a microcontroller or microprocessor could supply. In digital systems they switch signals on and off while in analog systems they are used to amplify signals. Transistors are one of the most versatile discrete components in electronics. Every engineer’s stock of go-to parts should have a few of each. Fear not, before wading through spec sheet after spec sheet consider using one of these general purpose transistors that are included in the ADALP2000 Analog Parts Kit. This can make answering the question “What transistor should I use?” potentially very confusing. ![]() When you need transistors for a project there are a multitude of choices. ![]() The best transistors to keep in your stock of parts ![]()
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