![]() ![]() ![]() The “better” description of these aspects of the device fills the heads of first-year electronic engineering students until they never want to hear about an h-paramater or the Ebers-Moll model of transistor function again in their entire lives. Of course the base-emitter junction is a diode and it is not a simple potentiometer that sits between collector and emitter. It’s a simple but effective way of explaining the basic operation of a transistor, but it stops short of some of the nuances of how a transistor works. If you wind back the base current, he drops it back. If you apply a little more base current, he pushes up the collector a bit. A transistor is shown as a room in which “transistor man” stands watching a dial showing the base current, while adjusting a potentiometer that limits the collector current. If it’s a resistor, just pop it out and increase/decrease the size of the resistor accordingly until you get the right voltage, then you can solder it in.If you open up the perennial favourite electronics textbook The Art Of Electronics and turn to the section on transistors, you will see a little cartoon. If it’s a trimmer – just slowly turn the dial and you’ll notice the voltage change either up/down – once you get to the right voltage, you’re done! You’ll notice a reading on your multimeter – this is the voltage being delivered to the COLLECTOR pin.ĭepending on the board and what the build guide says, you can/will need to adjust the trimmer/resistor to get the voltage correct – a lot of the time its a ballpark number and you can tune it by ear, if it sounds good when you play it…you’ve got it! Next, connect the positive lead (red) from the multimeter to the COLLECTOR pin of the transistor – it can be awkward doing this the first few times but you’ll get the hang of it. ![]() Set your multimeter to voltage reading (this is the V with a solid line, and a dotted line below it).Ĭonnect the negative lead (black) from the multimeter to a ground point on the board – this can be the main ground connection from the power, or the ground side of a resistor etc. You’ll need power and ground connected to your board to get the bias working – without power…you’ll get a zero reading…and yes…we’ve done that! The images below show a trimmer and a socketed resistor – both are feeding the collector pin of the transistor on the relative boards. If you have a fixed resistor ( just a standard resistor) – it’s a good idea to socket this first and you can swap and change resistors until you get the desired voltage to your collector pin. If you have a trimmer ( our boards use trimmers!), it’s easy to adjust the resistance just by turning the dial on the trimmer. That usually happens in one of 2 ways, either a fixed resistor or a trimmer. So the key to this is getting the right voltage into the transistor. Too much voltage – it also wont work properly. Too little voltage – it will be starved and wont work properly. The basics are like this, the transistor needs a certain level of voltage supplied to the COLLECTOR pin ( this varies per transistor so please check!) in order for the transistor to work. Now you have a multimeter, you’ve built your board…but you need to bias the transistor(s) – don’t panic, it’s actually easy! You can read a lifetimes worth of content in books and online about the calculations needed to accurately work out which resistor you need based on the datasheets of the particular transistor you’re using – but there’s an easier way! You’ll need a multimeter for this – we’ve been using Amazons own “Amazon Commercial 6000 Count Compact Digital Multimeter” which you can buy through the link – we can’t say its better than any other but we like it and it’s not let us down yet. ![]()
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