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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I’d sure like to see the documentation that claims this is the recommended value. Email Required, but never shown. The voltage V CEbetween the collector and emitter, is called the saturation voltage and is usually small enough to be neglected.

I’m glad you’ve done the calculations, that’s a good start.

BC637 – BC637 NPN High Current Transistor

This is a classic mistake. Why not add 3 common emitter switch? This is not the way to do it. 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.

Sign up using Facebook. 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.

BC Datasheet(PDF) – Fairchild Semiconductor

Emitter follower This can be seen as a current booster. Post as a guest Name. Spehro Pefhany k 4 It seemed superfluous at the time, but it makes a better answer. Post Your Answer Discard By clicking “Post Your Answer”, you acknowledge that you have read our updated terms of serviceprivacy policy and cookie policyand that your continued use of the website is subject to these policies.

The current gain varies a lot depending on all sorts of things: Thank you for the explanation, well i’m student in the area so i lack the expertise. The goal is to drive enough current through the base to make this happen. Essentially I stopped reading there.

  HP W1907 PDF

MOSFET switch Catasheet 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. Is my calculation correct?

You calculate the resistor value by looking up the 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.

ChetanBhargava He’s reading the minimum hFE, it goes up to The transistor will draw the absolute minimum amount of base current necessary to keep the right amount of current flowing through the collector. Sign up using Email and Password. 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.

The gain of the transistor is not well defined probably between 80 and Essentially you’ll use one of these circuits: Just to be clear, your suggested circuit will put way too much current through the LED, and it will be poorly controlled. A conservative number is one tenth of the current through the collector. A forced beta of 20 is usually good. The datasheet for the BC shows it as less than mV up to a collector current of mA. It would be awesome if we could, it would make many circuits simpler, but it’s simply too unreliable to be of any practical use.

Look at this spread from the datasheet: Common emitter switch This is the traditional “Transistor-as-a-switch” configuration, and is similar to what you have right now. As you can see, there is no base resistor.

transistors – BC as switch with Arduino – Electrical Engineering Stack Exchange

This can be seen as a current booster. 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.


Then you pick a base resistor to make sure the transistor is saturated. A circuit that relies on a specific current gain will simply not work well. If the 5V rail drops before the power to the Arduino, perhaps if they are powered from datashwet rails, all the current to the LED will come from the base, and thus from the Arduino. Sign up or log in Sign up using Google.

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 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.

I don’t have much experience with electronic components, and I would like to datasneet someone with more experience than me to check if my calculation is correct.

This works if the voltage drop across dataxheet LED is small enough that you have some “headroom” left across the resistor. Will it work the way I planned?

Rodrigo Peetz 10 3. The voltage at the emitter will closely track the voltage at the base, only 0. ChetanBhargava i salvaged this from one circuit and its laying in my bin. RodrigoPeetz Yes, no one will blame you or think less datasheef you for assuming that you can use the transistor in the way you wanted.

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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. I assumed that’s what he had in the junkbin. If your board has an unregulated input with a lot of ripple, you can use it directly.