BC637 DATASHEET PDF
BC, BC, BC High Current Transistors NPN Silicon Features. Base NPN Epitaxial Silicon Transistor Absolute Maximum Ratings Ta=25 C unless otherwise noted Symbol Parameter Value Units VCER Collector-Emitter Voltage at RBE=1K? : BC 45 V: BC 60 V: BC V. BC BC VCEO. Vdc. Collector – Base Voltage. BC BC BC VCBO dimensions section on page 4 of this data sheet. ORDERING. DATA SHEET. Product specification. Supersedes data of Apr Oct DISCRETE SEMICONDUCTORS. BC; BC; BC
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BC Datasheet(PDF) – Fairchild Semiconductor
I don’t have much experience with electronic components, and I would like to ask someone with more experience than me to check if my calculation is correct. Essentially I stopped reading there.
This is a classic mistake. The current gain varies a lot depending on all sorts of things: Look at this spread from the datasheet:. There must be hundreds, thousands of instructions out there on how to drive a LED with an Arduino, and the best method will be slightly different depending on the voltage drop across your LED.
Essentially you’ll use one of these circuits:. This can be seen as a current booster. The voltage at the emitter will closely track the voltage at the base, only 0.
You calculate the resistor value by looking up daatsheet voltage drop across the LED for the current you want, then observing that the voltage drop across the resistor will be the voltage from the Arduino pin minus 0.
This works if the voltage drop across the LED is small enough that you have some “headroom” left across the resistor. The voltage at the collector does not have any say in the current through the LED, which is another benefit.
If your board has an unregulated input with a lot of ripple, you can use it directly. As you can see, there is no base resistor.
BC637 Datasheet, Equivalent, Cross Reference Search
This is no omission from my part, and it is one of the benefits of this configuration: The transistor will draw the absolute minimum amount of base current necessary to keep the right amount of current flowing through the collector. A little warning however: If the 5V rail drops before the power to the Arduino, perhaps if they are powered from separate rails, all the current to the LED will come from the base, and thus from the Arduino.
This is the traditional “Transistor-as-a-switch” configuration, and is similar to what you have right now. The idea is however that the Arduino should drive the transistor fully on so it’s saturated, passing as much current as it can, or at least enough so that the transistor is not the limiting factor.
The goal is to drive enough current through the base to make this happen. A conservative number is one tenth of the current through the collector. Since the output from the Arduino will be close to 5 volt, and V BE can be treated roughly as a diode, you will have about 4. If you want to pass at most 20 mA through the collector, aim for 2 mA through the base, and you end up with a base resistor of about 2. The voltage V CEbetween the collector and emitter, is called the saturation voltage and is usually small enough to be neglected.
The datasheet for the BC shows it as less than mV up to a collector current of mA. This is perhaps the easiest to understand, because it’s as intuitive as the common emitter switch, but you only have to calculate the load resistor.
The series resistor at the gate is there to limit the switching current, and the resistor from gate to ground is there to make sure that the gate is not floating while the pin is in a high-impedance state that is, an input or turned off. This is not the way to do it.
The gain of the transistor is not well defined probably between 80 and It is better to add a series resistor on the LED – the forward voltage of a blue LED is probably around 3V, so the resistor drops 2V and at 22mA it would have to be about 91 ohms.
Home Questions Tags Users Unanswered. BC as switch with Arduino Ask Question. So using the formula: Is my calculation datashert Will it work the way I planned? Here bcc637 the datasheft schematic: Rodrigo Peetz 10 3. ChetanBhargava He’s reading the minimum hFE, it goes up to I’d sure like to see the documentation that claims this is the recommended bc6637.
I assumed that’s what he had in the junkbin.
That’s how I select transistors. ChetanBhargava i salvaged this from one circuit and its laying in my bin. I’m glad you’ve done the calculations, that’s a good start.
Look at this spread from the datasheet: A circuit that relies on a specific current gain will simply not work well. Essentially you’ll use one of these circuits: Emitter follower This can be seen as a current booster.
Common emitter switch This is the traditional “Transistor-as-a-switch” configuration, and is similar to what you have right now. MOSFET switch This is perhaps the easiest to understand, because it’s as intuitive as the common emitter switch, but you only have to calculate the load resistor. Why not add 3 common emitter switch? It bx637 superfluous at the time, but it makes a better answer. Thank you for the explanation, well i’m student in the area so i lack the expertise.
RodrigoPeetz Yes, no one will blame you or think less of you for assuming that you can use the transistor in the way you wanted. It would be awesome if we could, it would make many circuits simpler, but nc637 simply too unreliable to be of any practical use.
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