Hello All,
I want to amplify signal from sensor(sensor output: +/- 900 mV pk ) through LM7171 Op-Amp by configurating it as an inverting amplifier.
For that i have gone through the datasheet of LM7171. in datasheet, recommanded resistor value for feedback resistor is 510E.
i have choose 470E as a nearby value for feedback resistor. now i need the gain near by 5, so i have used 100E as a series input resistor for inverting terminal.
So, my practically gain is 4.7.
i want to use single supply, that is +12V.
so i have given half voltage reference bias, that is +6V at non inverting terminal.
now the problem is, when i disconnected sensor from LM7171, & check the output signal from sensor, it shows +/-900mV pk.
but when i connect this sensor with LM7171 inverting amplifier, my output signal from sensor( input signal to inverting terminal of Op-Amp) goes down within +/- 75mV pk. so my sensor output signal feels loading effect.
To remove this loading effect, i have to increase resistor value of both(input series resistor, feedback resistor) in kilo ohms(ex. 20K, 100K).
this may be work. but to use larger resistor value may produce other problems like noise etc.... i want to use only recommanded resistors as per datasheet.
So how can i use lower resistance value & remove loading effect from sensor by using only one Op-Amp? ( i do not want to use voltage follower as it needs dual supply)
please help me to solve this problem.
Thanks in Advance.
