A device is provided. The device includes an operational amplifier, an output circuit, a first capacitor, and a second capacitor. The operational amplifier is configured to generate an output according to a feedback signal. The output circuit is configured to generate a first current signal in response to a supply voltage and the output of the operational amplifier. The first current signal includes a first ripple signal. The first capacitor and the second capacitor are coupled in parallel between the operational amplifier and the output circuit. The first capacitor is configured to receive the first current signal and feedback to the operational amplifier the first ripple signal.