I/V Stage
Requirements for an IV stage :
- Maintain the DAC output voltage constant. This means a very low input impedance Zin (a few ohms) for the IV stage. Ideally Zin should be constant versus DAC output current value, and frequency, up to a few tens of MHz.
- Gracefully handle the current steps produced by the DAC, ie. don't get into slew rate overload etc.
- Be as linear as possible.
- Convert the DAC output current to a ground-referenced voltage (no referencing to V+ and crap PSRR)
- Use obtainable components, low power, and max +/- 15V rails
- Possibly provide balanced outputs from one unbalanced DAC
- Certainly handle differential current output DACs
- DAC output current is varies from 1 to 5 mA pk-pk depending on model
I already experimented with opamps versus transistor current steering topologies and I much prefer the sound of the second type.
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