I am trying to make a voltmeter with a 10-bit ADC. The ADC can measure only positive voltages so I have made an input stage with Operational Amplifiers.
The idea of the circuit is to transform any negative voltage to positive. V1
is the voltage output and V Detect
is 3.3V or 0V if the input signal is negative or positive, respectively.
The input frequency will not be more than 200 KHz. Will this circuit work ok whit the TL084? Is there any special parameter I should take into account?
Also I need V1
not to exceed 3.3V, will a zener diode work or it will cause any problems with regards to capacitance? I know ADC are very sensitive to any external capacitance because of the internal sample-hold capacitor they have.
Best Answer
Some observations:
Even worse, you then showed two of the parts with power and ground connected, and two without. What if the two pairs were connected to different power and ground voltages? That would be really misleading since it's not physically possible. This kind of schematic convention makes no sense and invites exactly the kind of confusion shown in point 1 above. I left that there so you can see what the first reaction to this misleading schematic was.