You have an inverting amp, a G = 1, a 1V input, so output
theoretically should go to - 1 V. But PSOC is a single supply
analog device, no pin can go below ground or above Vdd, actual
values in DC section of datasheet.
So if you want to interface to PSOC you have to offset Vin to
meet its single supply nature. Provide an offset to the NI input of
So what is the range of the input you want to supply to PSOC ?
You can use the equation here for Vout, set R2 to 0, R4 to infinity. www.electronics-tutorials.ws/opamp/opamp_5.html
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So in short bias the NI input of the OpAmp to Vdd / 2 with a pair of resistors.
Then if Vdd is 5 V as an example, for an input that goes from 0 - 5 V the
OpAmp output will go from 5 V to 0 V.
Another way of handling - input signals -
Note this technique of offsetting with R to Vdd allows
for - input signals and biasing up to Vdd / 2 for max input
CM range. Also eliminates expensive coupling cap if doing
an AC coupled design. Use the Excel calculator in zip file
I posted to determine R values. One negative is input Z be-
comes the sum of the two Rs used for offsetting.
Use the Excel calculator in the zip file to calc Rs.
Sorry for the late reply.
I didnt know that the OpAmps on the PSoC were single supply. Providing an offset to the NI input of the OpAmp as you suggested worked perfectly.
Thanks a lot, Dana.
Glad I could help.