hello voltnuts,
I've just gotten back into hobby electronics and would like to have a go at building a reasonably good voltage reference. Mostly to practice my fundamentals and to have something that may be useful in the future.
I've been reading around the last few days and would like to ask some theory questions to get your expert answers and make sure I'm understanding what I'm reading. Apologies for it being a bit of a brain dump but I feel like I'm trying to process a lot of information at the moment and not sure yet how it all comes together.
The main variables we're trying to control with a voltage reference are noise and drift. Is there anything else that needs controlling?
1. The major factors contributing to noise are the components themselves and "outside world" interference. Which is dominant?
2. The major drift factors are time, temperature and humidity. Are there any others?
Design considerations:
Supply voltage: The supply to the voltage reference should be stable. Would using another voltage reference with a suitable output current be a good option for this?
Temperature control: If one were to try and control the temperature with power resistors for example. Using a micro controller controlling a current source. Would this potentially introduce noise beyond the usefulness of maintaining temperature control?
Buffering: What are the advantages of buffering the output of a reference? Surely this just introduces more potential noise and error sources?
Practical implementation:
I've seen slots used in PCB design to minimise physical stress on the reference part while also isolating from other PCB signals & potential noise sources. Is this always a good idea?
EMI: Is the easiest way to deal with this throwing it in a metal project box?
PCB ground plane. Is this a good idea around the reference to reduce noise?
Trace length and width - longer traces will pick up more EMI. Wider traces have more impedance and capacitance. So keep them short and thin?
Thanks in advance.