A circuit for sampling an analog input signal may include a transistor disposed on a substrate and a sampling capacitor coupled to one of the source and the drain of the transistor. The transistor may be disposed on a substrate that is coupled to ground. A source and a drain of the transistor may be disposed in a back gate of the transistor. The analog input may be supplied to one of the source and the drain of the transistor, and the back gate may receive a back gate voltage having a value that is lower than ground.