I think you missed Mooly's point. How much current you need to change through the diodes for 50mV change in voltage drop?
Jan
Jan
Thanks Jan, that's it exactly 🙂
50mv per diode doesn't sound like much but it is enough to change the current in the emitter. This is a simplified version based on Dougs circuit. The only thing that has changed between left and right is the resistor biasing the diodes. You can see the resulting change in the forward voltage dropped across each diode and yet the forward biased B-E junction shows a remarkably small change.

(I just tried a 2N3055 for curiosity, and that throws up a slightly unexpected result 😉)
R3 is for biasing current in diodes only.That shouldn't change the voltage drop across diodes that much.
50mv per diode doesn't sound like much but it is enough to change the current in the emitter. This is a simplified version based on Dougs circuit. The only thing that has changed between left and right is the resistor biasing the diodes. You can see the resulting change in the forward voltage dropped across each diode and yet the forward biased B-E junction shows a remarkably small change.

(I just tried a 2N3055 for curiosity, and that throws up a slightly unexpected result 😉)
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