Testing the source/sink regulation and compliance clamps
There are four output op-amps configured as precision diodes. Depending upon whether an input reference is held high or low, two of the four op-amps are potentially active. The arrangement provides an extra bit of precision to the DAC output for voltage and current control. It also centers a 0V output around Gnd, which avoids the offset trim that would be required to turn the unipolar DAC into a bipolar output.
All the op-amps work as non-amplified difference/summers and the circuit will need a later gain stage.
The resistor dividers need to be upgraded to have lower tempco.
First hand-etched two-layer board!
All the PCB drilling needed for vias is a pain. Probably went overboard with decoupling caps!