Hey all,
I hope I'm not repeating something someone else has posted already, but if I am, please let me know.
I'm trying to amplify a DC signal on the order of microvolts (tens of microvolts at times, thus it needs programmable gain). I've tried using auto-zeroing amplifiers (the AD857x series to be exact), but they seem to only take GND and +5 as power supplies and thus do not allow negative signals (they also can't be made into inverters for some reason...).
Second, I tried using reed relays to take the DC signal and make it into a square wave. But, that didn't work either since (as you probably know) there's noise whenever the relays switch, if you go above about 1 Hz, even if you use another relay to short the inputs whilst other relays commute the leads.
Anyways, I then tried using ADG453 chips (semiconductor swithces, basically), but I can't seem to get that circuit to act reliably. Sometimes it switches according to my logic signal, sometimes not. But it definitely will not switch the signal's polarity: it just grounds the signal. The problem with semiconductors (beyond them not working) is that they have thermal emf's that one must worry about, which are on the order of tens of microvolts, so that's a no-go probably.
In short, I'm out of ideas. Any and all help would be immensely appreciated.
I hope I'm not repeating something someone else has posted already, but if I am, please let me know.
I'm trying to amplify a DC signal on the order of microvolts (tens of microvolts at times, thus it needs programmable gain). I've tried using auto-zeroing amplifiers (the AD857x series to be exact), but they seem to only take GND and +5 as power supplies and thus do not allow negative signals (they also can't be made into inverters for some reason...).
Second, I tried using reed relays to take the DC signal and make it into a square wave. But, that didn't work either since (as you probably know) there's noise whenever the relays switch, if you go above about 1 Hz, even if you use another relay to short the inputs whilst other relays commute the leads.
Anyways, I then tried using ADG453 chips (semiconductor swithces, basically), but I can't seem to get that circuit to act reliably. Sometimes it switches according to my logic signal, sometimes not. But it definitely will not switch the signal's polarity: it just grounds the signal. The problem with semiconductors (beyond them not working) is that they have thermal emf's that one must worry about, which are on the order of tens of microvolts, so that's a no-go probably.
In short, I'm out of ideas. Any and all help would be immensely appreciated.