Noise filter

A system for regulating a voltage, the system comprising:

• a low-dropout voltage regulator (LDO) configured to compare a filtered reference voltage to an output voltage;
• a voltage reference configured to generate an unfiltered reference voltage;
• and
• a noise filter configured to receive the unfiltered reference voltage and to generate the filtered reference voltage, the noise filter including:
• a first transistor coupled between an input terminal and a bulk node, the first transistor having a first gate terminal coupled to the input terminal and a first body terminal coupled to the bulk node;
• a first capacitor coupled between the bulk node and a ground;
• a second transistor coupled between the bulk node and an output terminal, the second transistor having a second gate terminal coupled to the output terminal and a second body terminal coupled to the bulk node;
• and
• a second capacitor coupled between the output terminal and the ground.

A method for noise filtering, comprising:

• receiving an input voltage at a noise filter, the noise filter including a capacitance and a first resistance generated by a first transistor and a second resistance generated by a second transistor;
• configuring the first resistance lower than the second resistance to increase a charging rate of the capacitance when the input voltage is made larger than an output voltage;
• and
• configuring the resistances provided by the first transistor and the second transistor first resistance higher than the second resistance to decrease a discharging rate of the capacitance when the input voltage is made smaller than the output voltage.