hallo guys..
hope you have time to answer newbie question..
i follow attached schematic, but i change the op-amp to AD620 and the input voltage is 2 volts before voltage divider (r1 and r2)..hence input to opamp is 0.5 volts ideally
i was expecting output is the same as the input..but no matter how i change the input, i always lost 0.5-0.6 v on the output, do you have any idea why?
That is a 2:1 divider on the input so for 2v before the divider, you should have 1v at the summing point between the two resistors which should match the output from the buffer (op-amp). (this is assuming the input to the buffer is within the range of the op-amp - above the negative side and below the positive side.
When you hook this up, what is the voltage you measure on the output? It should be 1 volt as gpsmikey said, not half a volt.
(By the way, convention says to swap your diagram left & right.)
gpsmikey:
That is a 2:1 divider on the input so for 2v before the divider, you should have 1v at the summing point between the two resistors which should match the output from the buffer (op-amp). (this is assuming the input to the buffer is within the range of the op-amp - above the negative side and below the positive side.
A minor correction, there is no summing point. A summing point is held at virtual ground and has multiple
currents feeding it to be summed: http://www.electronics-tutorials.ws/opamp/opamp_4.html
giri_ginanjar:
i was expecting output is the same as the input..but no matter how i change the input, i always lost 0.5-0.6 v on the output, do you have any idea why?
The AD620 is not rail-to-rail, you must provide a separate negative supply if using signals near 0V.