Hi
I am using LM2904 IC as Non inverting opamp to increase the range. Op amp input voltage range is 1.44V to 2V and output should vary from 0 to 3.2 V to supply to micro. The Vdd of the opamp is 5V. How to select the resistor values for the non-inverting configuration. And please suggest RC filter values for the input and output(( because 10 percent of 50hz ripple is there in input)
Hello Hema,
The Excel Calculator in this e2e FAQ is helpful. [FAQ] Voltage scaling for almost any application (single ended)
Add capacitor from VCM to ground to filter 50Hz. Set a cutoff value above your signal bandwidth and well below 50Hz ; if this is not possible, consider adding a notch filter set to 50Hz (will 60Hz ever be an issue). For VOUT to micro ADC you can add another low pass filter.
Do you have a refence voltage more accurate (than 5V supply) or more correlated to ADC reference? If yes use that as a reference instead.
| RF | 100,000 | Ω |
| RG | 32,588 | Ω |
| RH | 60,764 | Ω |
| VREF | 5 | V |
For a closer to 0V output, use LM2904B or increase all resistance above.
VOL is varies with sinking current IOL ; see application note: Design Guidelines for Devices with LM324/LM358 Cores
