Respect sir:
Good day,
Please look at the following circuit ,the pressure drop of the lamp is 9v while the working current is 60mA. It required that using constant current to work.Calculting the value of R3 and R1.
http://www.noelshack.com/2017-22-1496221820-4-19-3.png
The voltage of pin13/14/15 when ULN2003 that I bought from internet (http://www.kynix.com/Detail/376871/ULN2003.html ) is 0.7V , the voltage of transistor base b is 3.1V and the c is 3V. The voltage of emitter is 2.4V. I would like to ask the following questions:
1). Is the R3 =(2.4-0.7)/0.06?
2). If the triode is in the saturation region ,shouldn’t the ce pressure drop be 0.3v? Why it’s 0.7v here?
3). If the work is in the amplifier region,how to guarantee that lamp work in the constant current--60mA ?
4). What references related to stable diode should I note when calculating the value of R1?
Best regards~
