Insrumentation Amplifiers Help

[Brian Deese]

I linked an AES presentation above, but here it is again: http://www.thatcorp.com/datashts/AES...ic_Preamps.pdf

Close matching of components is fine if you need to maintain amplification down to DC, but point is that you do not have to. There are a few solutions in that document that actually work. If you put large enough capacitor in between the transistors' emitters, you are relieved of the transistor matching, and the rest of the story becomes easy.

That is a swell article,I may have that printed.The 33uF caps they use,do you think they are electrolytic? Thats a pretty big cap.

[Thomas]

I had a good long read today,I have a question regarding analog ground. In the book Inside the metal detector,on the PI designs there is a voltage divider and an opamp that supplies analog ground 1/2 battery voltage.Now on my battery that I plan to use for my project the cells are exposed and I can get to the center of the battery no problem.I can solder directly to it and take it to the board.Which is better? I can see it either way. I am going to guess divider and amp is better because if one of the cells discharges slightly more on one side then my voltage will not be in the center anymore,correct? Its a li-ion batt with four cells, btw.

http://www.diyaudio.com/forums/power...1-25v-20v.html

[Davor]

That is a swell article,I may have that printed.The 33uF caps they use,do you think they are electrolytic? Thats a pretty big cap.

It must be a non-polarised electrolytic cap. They are also referred to as bipolar. You'll find them quite cheap up to about 100uF. If you can chose, pick a low ESR or low impedance type.