Assistance calculating Transistor

ericgibbs

Joined Jan 29, 2010
14,189
hi,
As most of the LED's you are using at 2Vfwd, why don't you connect 2 off 2Vfwd in series when powered from 5V via a resistor, much more efficient.
E
 

dl324

Joined Mar 30, 2015
13,535
I think my math is correct but I am not sure. I believe all the info is in the image.
  1. The transistor will not have a beta of 300 when used in saturation mode.
  2. What is the output drive capability of the controller?
  3. You drew the transistor sideways.
  4. We always draw GND pointing down.
  5. As mentioned, if you put two LEDs in series, you'll waste less power in current limiting resistors.
  6. Do you really need to operate the LEDs at 20mA?
clipimage.jpg
 

Thread Starter

Stupdiav

Joined Jul 29, 2011
12
hi,
As most of the LED's you are using at 2Vfwd, why don't you connect 2 off 2Vfwd in series when powered from 5V via a resistor, much more efficient.
E
This is just a small part of a larger project, each one is actually driven from various switches and things, giving a indication of an input. The purpose of the transistor is to give the ability to disable / shut them off when not desired.
 
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