Lindy Mayfield wrote:
> The way I understand Q1 or transistors are as switches: a small current
> that controls a larger current from Current to Emitter.  I don't see
> that on/off part here in the circuit.

Right.  Transistors are inherently analog devices.  They can be slammed on
and off hard to act like switches in some applications, but that's not what
is happening here.

Go back to the basics of bipolar transistors.  It might help to try to get a
rough idea of the emitter voltage as 100uA are drawn from it, then 1mA, then
10mA.  Use 100 for the gain of this transistor and calculate the currents
for each case.


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