harlow there, if i have a voltage range from 0.6 volts to 1.4 volts, can i use transistor to switch on a typical LED which has the forward voltage at round 2 volts?

If cannot, how can i do that?

Thanks in advance :wink:

Desmond.

 

Are you saying you have an input voltage of 0.6V to 1.4V? Is there a supply that you can use too?

 

the supply i used actually is 5 volt, but due to a circuit there, the output i have is 0.6volt to 1.4volt (the range) ...

then i would like to prove that the voltage there is not 0 so i am thinking to use LED as the indicator.

so do you think 0.6volt (we take the minimum) can switch on a LED by using transistor? maybe bjt or mosfet? or what should i do?

Thanks.

Desmond

__________________
Regards,
Desmond

 

The problem is that 0.6V is just a little lower than the Vbe for most BJTs. I'll think about it a bit more and get back to you .

 

If you're not adverse to using an op-amp, it would get a lot easier

 

yeah .. i am thinking the same way too

i will try it out with LM751 first lar ..

thanks man ~ :wink:

__________________
Regards,
Desmond

 

The LM331 is a component I have enjoyed lately. Maybe it would be handy for you. It comes in a convenient SOT-5 package.

j.