Technical question about good low power rail to rail opamp. I published 'scope_pic'
The question is how to make a 1 MOhm, few pF, input with a bandwidth of about
1MHz, with as few components as possible, that also creates a +2V DC offset (to get the ADC midrange and allow negative signals),Now My first idea was to make a JFET input, tried something in spice like this: ftp://panteltje.com/pub/fet.gif
There is a lot of spread in individual jfets, and the only negative voltage available is a tap of the -8 V from a MAX232.
So that leaves opamps, and the ones I found (5V rail to rail) have either low bandwidth, bad slew rates, incredible distortion, or all of those at the same time.
So I am looking for a decent quad 5V to 12 supply opamp with low current draw, only needs to drive a PIC input, say 10k in 25 pF, with low distortion, high gain, slew rate > 10V us, voltage swing to very near the positive supply, input impedance 00, input cap < 10 pF.
I looked at LMC6036, some others, but no good. Any ideas? So it is for the scope input amp.