I'm trying to understand the attached schematic, which I came across when repairing an oscilloscope.
Am I right in thinking that this circuit is regulating VCC (5V) down to 3.3 and 2.5 volts? Why does the opamp use 12v rails rather than 5volts?
The non-inverting input to the opamp seems to be a voltage divider. I take this divider is used to provide a simple voltage reference?
Given that this is in an oscilloscope (a LeCroy LT342) is there any reason to use an opamp here rather than a voltage regulator?
One further thing that confuses me, is that on the board Q9 is not fitted, and has been replaced with a short between 2 of the pins. I can't understand how the circuit can work in this scenario, can anyone cast any light on this?
From my naive understanding, this seems like a bad design, and that it would be preferable to use a voltage regulator. What designed decisions might I have missed here?