where does this voltage come from?

can anyone tell me where this voltage comes from? I've run into this schematic different places, and I don't know how on two parallel legs you can have 2 different voltages... on one leg there is a 30V power source... how can you have 10V on a parallel leg? On one image it's referred to as the bias voltage, on the other it's called out as ~10V....

much thanks!

hi,
The 30V is for driving the constant current, so the 30V will not be present on the 10V rail, only the constant current will flow into the 10V load.
If you examine the circuits you will see the 10V is the result of the CC drive.

There is a 4 milliamp constant current device letting 4 milliamps into that line. The 10 volt measurement is saying that the resistance across the amplifier must be about 2500 ohms.

No intent to insult sir Eric. Just re-wording his answer in case it makes better sense to the OP.

Much thanks for the answers, yes it does make sense now... I was thinking that if the current regulator is a diode that regulates 4mA @ 1V across it, and then there's a 30V source in series with it, that the voltage across that leg would have to be... well 30V.... but it makes sense if it's pumping 4mA into the other leg that the resistance of the other leg could result in a smaller voltage

thanks!