Using multiple supply voltages

[Mark Hammer]

Supposing I have a circuit where I decide that I want to use different supply voltages for different parts of the circuit.  For example if I had a circuit that used several different types of semiconductors - opamps, germanium transistors and FETs - and for whatever reasons felt that the circuit was best served by giving them each a different supply voltage so as to extract their quirks.  What are the comparative advantages and disadvantages to using the same Vref throughout?  Is a simple DC-blocking cap enough to allow me the freedom to use different Vrefs in different parts of the circuit?

[PerroGrande]

Hi Mark,

If I understand you correctly, you're looking to provide various different reference voltages for use in different places throughout your circuit. 

As long as they all share the same ground, and each part of the circuit that is AC-Coupled has appropriate ground return paths, this shouldn't be an issue.  We really do this all the time when we use pots to set bias voltages, etc.

[Sir H C]

The most important thing is to make sure that the supplies go up and down in a way that doesn't cause things to get reverse voltage and get stressed. 

For the reference, so long as it is within the range of all the supplies you wish to use it with, and with good isolation you should be fine.