Hello can somebody tell me, how come 10mA this current source

[michael1978]

can somebody tell me this circuits calculations, how come 10mA
please

 

[Audioguru]

The base-emitter voltage of the 2N5401 Q6 is about 0.62V when it begins to turn on. When Q6 turns on it begins to cutoff Q7 so the current in R9 and Q7 is constant at 0.62V/62 ohms= 10mA.

 

[michael1978]

The base-emitter voltage of the 2N5401 Q6 is about 0.62V when it begins to turn on. When Q6 turns on it begins to cutoff Q7 so the current in R9 and Q7 is constant at 0.62V/62 ohms= 10mA.

ooohh thank you very much

 

[Terry01]

The base-emitter voltage of the 2N5401 Q6 is about 0.62V when it begins to turn on. When Q6 turns on it begins to cutoff Q7 so the current in R9 and Q7 is constant at 0.62V/62 ohms= 10mA.

I guessed the answer was to do with the transistors before I got to see Audioguru's detailed answer to the question.
I didn't know the exact numbers but I guessed that was where the 10mA reading was coming from.
I am learning

 

[michael1978]

I guessed the answer was to do with the transistors before I got to see Audioguru's detailed answer to the question.
I didn't know the exact numbers but I guessed that was where the 10mA reading was coming from.
I am learning

yes 10mA audioguru
answer

 

[Terry01]

We will learn a lot from the more experienced guys Michael. I have learned a lot by just reading other peoples posts.

 

[AnalogKid]

Note that the schematic in post #1 has a problem. The high impedance and high compliance 10 mA output point is not the emitter of Q7. It is between the collector of Q7 and ground. If you want the 10 mA to go off and do something like light an LED, that is where to connect it.

ak

 

[michael1978]

We will learn a lot from the more experienced guys Michael. I have learned a lot by just reading other peoples posts.

yes that is ture, thnx the forums