I want to develop an amplifier circuit which allows me to map an input voltage from -8 to +12 V to a suitable range for an ADC (0-3 V).
While searching the internet I found only a few suitable circuits. Therefore I assume that I use the wrong search terms. I assume that this application occurs frequently, e.g. the voltage measurement of general AC sources or motor voltages etc.
Since the gain is less than 1, I have found two possible solutions so far:
Voltage divider + non-inverting amplifier with DC offset
Inverting amplifier with positive DC offset
However, I can't judge which is better or suitable at all in my situation. Therefore I am looking for sources (application notes) for such amplifier circuits.
How can I map an AC signal to a small output signal with an DC offset?
Here are some more details.
The signal we want to measure is a bus signal which corresponds approximately to the RS-485 standard, with some exceptions. We want to sample this signal with about 2 Msps which corresponds to 8 samples at a data rate of 250 kbps. The goal is to make a statement about the quality of the signal.
The amplitude resolution does not have to be very precise, but qualitative statements should be made. The goal is 6-8 significant bits.
The two signals of the bus should not be sampled differentially but measured separately against GND to be able to make a statement about the offset to GND.
For the supply of the amplifier circuit only a supply voltage of 3.3 V is available and no further supply voltage is planned.