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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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. 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.
Email Required, but never shown. Essentially I stopped reading there. Common emitter switch This is the traditional “Transistor-as-a-switch” configuration, and is similar to what you have right now. This is no omission from my part, and it is one of the benefits of this configuration: This works if the voltage drop across the LED is small enough that you have some “headroom” left across the resistor. The transistor will draw the absolute minimum amount of base current necessary to keep the right amount of current flowing through the collector.
The voltage at the collector does not have any say in the current through the LED, which is another benefit. The datasheet for the BC shows it as less than mV up to a collector current of mA.
Look at this spread from the datasheet:.
(PDF) BC637 Datasheet download
Here is the simplified schematic: Why not add 3 common emitter switch? Then you pick a base resistor to make sure the transistor is saturated. So using the formula: 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 current gain varies a lot depending on all sorts of things: Essentially you’ll use one of these circuits: Sign up using Facebook. 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. I’d sure like to see the documentation that claims this is the recommended value. Is my calculation correct? It seemed superfluous at the time, but it makes a better answer.
The voltage V CEbetween the collector and emitter, is called the saturation voltage and is usually small enough to be neglected. I assumed that’s what he had in the junkbin. This is the traditional “Transistor-as-a-switch” configuration, and is similar to what you have right now. 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.
Home Questions Tags Users Unanswered. 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.
Sign up or log in Sign up using Google. A circuit that relies on a specific current gain will simply not work well. Essentially you’ll use one of these circuits:.
There must be datasneet, 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. Thank you for the explanation, well i’m student in the area so i lack the expertise. A forced beta of 20 is usually good. Sign up using Email and Password. The gain of the transistor is not well defined probably between 80 and A little warning however: That’s how I select datashewt.
As you can see, there is no base resistor.
BC Datasheet, Equivalent, Cross Reference Search. Transistor Catalog
Rodrigo Peetz 10 3.
This is not the way to do it. 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.
BC637 – BC637 NPN High Current Transistor
Emitter follower This can be seen as a current booster. 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. This is a classic mistake. A conservative number is one tenth of the current through the collector.