How would you go about generating a 1V source in a project?
A voltage divider from the 12v rail would work, but the signal would have any noise that the rail already has.
A voltage regulator like the TLV73310 will work, but I’d need to regulate from 12 to 5 first, which seems like an overkill to me.
Any other ideas?
1 Like
A lot of the DIY video designs use the TL431 to generate a 2.5V reference voltage, you could then use a 5:2 potential divider to get it down to 1V, maybe throw a buffer in there too. The TL431 can run off up to 36V I think?
2 Likes
Thanks for answering 
Im using that voltage reference already in my design, I just thought it may not be suitable for a current source. But throwing a buffer and then the voltage probably does the trick. Or would you rather do it the other way around; Voltage divider and then buffer?
1 Like
For some of my designs, I need several references like 2.5V, -2.5V and 1.0V. As long as you buffer the source from large resistive and capacitive loads, you can divide it how you like. The unity gain buffer will fight tooth and nail to ensure It’s output matches the +input regardless of what you connect afterward.
Here are a few examples. I added a few capacitors arbitrability for filtering.
There are of course alternate voltage refences and other low-noise op amps available; these are simply tried-and-true.
5 Likes
With my Experimentation board I use a 78l05 and a resistor voltage divider
4 Likes
Linear voltage regulators, such as the 7805, are also very low-noise in design. They use a ripple rejection feedback loop and offer significantly more current than a dedicated voltage reference.
They have a larger margin of error though, like +/- 4%; but that is absolute maximum.
I also use a 7805 and voltage divider on SHUTTER for one of the references and the measured output was 1.00V with 1% resistors!
3 Likes
I’d put the buffer after the 1V reference, in theory no current flows into the op amp so you don’t need to worry about the reference being a suitable current source, just ensure the op amp can push enough current for your requirements
2 Likes
Perfect!
Thanks a lot.
The second example is exactly what I needed, I had half a tl072 unused and looking sad in my design.
I think the ‘why’ to use buffers is starting to click in my head.
Does the capacitor need to be electrolytic, or a simple ceramic would work as well?
1 Like
Takes a while to click! The EEVblog Op Amp tutorial is one my favourites for reminding myself about op amps EEVblog #600 - OpAmps Tutorial - What is an Operational Amplifier? - YouTube
The capacitor is a decoupling capacitor, should be ceramic and positioned as close to the IC as possible.
2 Likes