It's me again, after solving my switch problem I have another question.
I am looking at a Digital Pot to provide programmable gain and need to know the performance at the lowest and highest end of the wider. It is a 8 bit digital pot (10k resistor) and I programmed it to see if I indeed can get a gain of 255 (maximum) with it hooked up in an opamp inverting configuration.
Gain = (256 - x) / x
But after putting in 10 mV, I get a output of about -2V ... which is a gain of about 200. An input of 1mv gives me an output of -150mV. This is kind of confusing me.
I looked at the data sheet and it says under Analog Resistor Characteristics, "Absolute Linearity" and "Relative Linearity" with Units LSB (Lowest Significant Bit), does this information help me understand what is going on? Can someone help me understand why I don't get a gain of 255 and why I don't have consistant gain by increasing the input from 1mV to 10 mV?
Data Sheet: http://datasheets.maxim-ic.com/en/ds/DS1868.pdf
Page 9
Thank you.
Dru
I am looking at a Digital Pot to provide programmable gain and need to know the performance at the lowest and highest end of the wider. It is a 8 bit digital pot (10k resistor) and I programmed it to see if I indeed can get a gain of 255 (maximum) with it hooked up in an opamp inverting configuration.
Gain = (256 - x) / x
But after putting in 10 mV, I get a output of about -2V ... which is a gain of about 200. An input of 1mv gives me an output of -150mV. This is kind of confusing me.
I looked at the data sheet and it says under Analog Resistor Characteristics, "Absolute Linearity" and "Relative Linearity" with Units LSB (Lowest Significant Bit), does this information help me understand what is going on? Can someone help me understand why I don't get a gain of 255 and why I don't have consistant gain by increasing the input from 1mV to 10 mV?
Data Sheet: http://datasheets.maxim-ic.com/en/ds/DS1868.pdf
Page 9
Thank you.
Dru