When designing a circuit in subthreshold (for example a startup circuit), is it necessary to first design it by using a standard supply in 1.8V?

[Desmonday]

Additional Question:

Perhaps you are able to design it in 1.8V and operated the MOSFETs in saturation, should the design schematic be altered or changed if it is to be operated at subthreshold for example at 0.5V supply?

 

[dick_freebird]

That depends on the "organ donor" design. If
a 1.8V bandgap is done in the classic style,
no way is it sensible for 0.5V. You'd fold more,
probably work differential and what's a
common sub-bandgap reference voltage
the cool kids like these days anyhow?

 

[Desmonday]

Thank you dick_freebird. I have no idea, but your explanation helps.