![]() ![]() After finding a range of transistors that offered a wide variety of voltages and currents, I then filtered my options by choosing transistors also available in a through-hole package. ![]() I selected the components below by looking first at the most stocked NPN and PNP components on Mouser, Digi-Key, TME and Farnell UK. It's probably unlikely that you approach the transition frequency with a project built on a breadboard, however if you need a fast response from the transistor it could give you a decisive metric to use for deciding between similar transistors. This is the most commonly used parameter with which to compare the frequency response of a bipolar junction transistor-the frequency at which its short circuit current gain drops to unity. Your design should ensure you stay within the power rating of the device, or it may overheat and either fail or have degraded performance. The TO-92 package, which most assortment kits use, is typically limited to around 625MW, but some devices will have significantly lower or slightly higher maximums. Pd is the maximum power dissipation the device is capable of. Ic is the maximum current you can pass through the transistor, as long as it is within the power limit of the device. If your circuit will have inductive loads which could create transient voltages higher than Vce, you should place a TVS diode next to the source of the transient spikes to clamp the maximum voltage to lower than Vce of the transistor. Vce - Voltage - Collector to Emitter Breakdown (Max)Īs long as the maximum supply voltage the transistor will experience is lower than Vce and there is no circuity which could create high voltage transients (such as inductors, motors, solenoids), this specification is going to have little bearing on your circuit. We’ll select a small quantity of common components with good specs that will be versatile in many designs. We’ll also be looking at a smaller range of components than your typical 10, 12, and 24 value assortment kits, as many of those components have very similar ratings. There are many other specifications which may be considered important or even critical depending on your design, yet typically, these are going to be the most common parameters you will be selecting a device based on. If you have any suggestions for parts you regularly find handy, leave a comment below! Bipolar Junction Transistorsīefore we get to selecting parts, let’s quickly go over the important specifications for a bipolar junction transistor and what they mean. Ideally, the components we select here should be available in both through-hole, for prototyping, and surface-mount, for production. Even if you are not going to mass produce a board based on your prototype, it's nice to be able to build a circuit board using components that are available outside of part assortment kits. If we prototype a great new product on a breadboard, we want to ensure that we can build it as designed, rather than having to substitute in more modern components, which may have different performance parameters. ![]() ![]() We want to choose active, commonly stocked parts, as we might need to use them in volume in a design. I’m working under the expectation that if Digi-Key, Mouser, and the like have hundreds of thousands if not millions of a particular part in stock, it’s likely to be a popular part and not about to go obsolete. In this post, we’ll look at building our own assortment kit of through-hole BJT and MOSFETs which are very well stocked by major suppliers. Several of the transistors in these kits have long been obsolete, and they seem to be distinguished by having fewer options for MOSFET assortment kits, at least in the United Kingdom. In my previous article, Part Assortments: Bipolar Junction Transistors, I talked about buying bipolar junction transistor assortment kits from online marketplaces to stock up my prototyping supplies. ![]()
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