Why would you want to use 5V amps in a 24V circuit in the first place?
Good question! First of all I need a chopper amp for current sense. I watched Dave's videos of uCurrent and I thought I have 2 options - either get a chopper amp or do auto offset voltage compensation periodically. So I chose the easier way - chopper amp and I couldn't find one that can take higher supply voltage. Currently I'm not sure if I need the +/-12V either. In any case I'll need about +/-2 V around ground.
But if you suggest a good chopper amp that works with at least +/-9V it would be nice. The biggest problem would be offset drift with temperature and over time, because I'll use it with high gain for current sensing. Initial value of the voltage offset won't be a problem - I can null it in software.
Ow, and if I get rid of the 5V amps I'll need some very low input bias current opamps, so I can use 10MOhm voltage divider. In 5V I would use microchip's MCP601 to MCP609.
Nonono, see,
why do you think you need a chopper amp -- what Vos max spec do you need? What's the tradeoff?
There's always a spec, and there's always a tradeoff.
If it's current sense, then you can use stupidly high input bias bipolar types, which can be trimmed to better than 50uV. Chopper amps, being CMOS, also have very low input bias, which you won't need. Of course, if you get both, that's still fine.
You can also increase the gain of the shunt, at the expense of more power. It's pretty normal to spend a few watts there, especially if it doesn't matter (e.g., linear supply).
Examples:
Digikey SearchYou can also use resistor dividers to bring Vcm down, but this reduces differential gain, making the whole thing that much more noisy and sensitive to Vos. So that you'd have to use a chopper amp. Self-fullfilling prophecy. But you have to use ppm range resistors to get the CMRR anywhere near as good, which is more expensive than even a $5 op-amp, let alone a proper current sense amp device with good CMRR and stable gain. So it gets really messy, really fast.
Far be it for me to recommend a Maxim part, but their products place highly in this search:
http://www.digikey.com/product-detail/en/MAX9943AUA%2B/MAX9943AUA%2B-ND/206204150uV Vos, pretty ordinary otherwise. Fast enough for DC current sense, but you'd want something faster (give or take how much gain you need) for use in a switching supply loop.
http://www.digikey.com/product-detail/en/MAX44248ASA%2B/MAX44248ASA%2B-ND/3829285Relatively noisy, but no 1/f noise; low Vos, wide supply range. Also on the slow side. Not rail to rail. Autozero is related to chopper; you'd have to look up their patents to see the difference and mechanism.
http://www.digikey.com/product-detail/en/OPA180IDGKT/296-37995-1-ND/4948940Rail-to-rail output, low noise, apparently a true chopper.
http://www.digikey.com/product-detail/en/TLE2037CD/296-10386-5-ND/380956Very fast (non unity gain stable), low noise, low offset, good enough to use in a switching loop.
Now that I'm salivating, I think I shall store this list for future, uh, use...
Tim