The disclosure describes devices and methods for starting up a microphone assembly. The device may be implemented on an integrated circuit that includes a direct current (DC) bias circuit. The DC bias circuit may be coupled to a transducer and configured to supply a DC bias signal to the transducer. The DC bias circuit includes a multi-stage charge pump and a low pass filter (LPF) circuit. The LPF circuit includes an adjustable resistance and a capacitor. A resistance of the adjustable resistance may be reduced to reduce the settling time of the LPF while starting (e.g., turning on) the microphone assembly.