Hi,
I had made a simple buffer circuit from the TLC2272 (V+= 3.3V, V-=0 ) . The input to the IN+1 pin is +1.25V DC from a 100k potentiometer. The output shows the DC voltage (1.25V) + a 100mV pk-pk noise with a frequency of 1Mhz. We had to eventually add a 2.2uF capacitor to attenuate the noise to a manageable output, but this is very odd and can identify where the noise is coupling from!
Regards,
Tony
The dominant source of the noise within your circuit will be 100k potentiometer. The thermal noise spectral density of the 100k potentiometer is 40nV/rt-Hz, Vnr=(4*kTR)^.5, so you need to integrate the spectral density noise across the unity-gain noise bandwidth: Vn_rms=Vnr*(BWn)^.5=Vnr*(1.57*2.2MHz)^.5 = 74uVrms or 471uVpp – see the link below to TI precision labs training website. However, since the calculated noise is nowhere near of what you see, the most likely reason for it is that it is fed from the noisy power supply – do you use a switching supply voltage? If so, you need to add a large bypass capacitor (~1uF) between the rails right on the supply pins.
