The present disclosure provides a neuromodulation device that comprises at least one amplifier circuit that suppresses a common mode (CM) voltage signal in the input voltage signal. The amplifier circuit comprises an input stage to receive the input voltage signal, and a differential transconductor to provide an output current signal based on a DM voltage signal in the input voltage signal. The transconductor is provides a first CM voltage signal tapped after a non-inverting input, and a second CM voltage signal tapped after am inverting input, to CM amplifier of the amplifier circuit. The CM amplifier combines the first CM voltage signal with the second CM voltage signal, amplifies the combined CM voltage signal with an inverting gain, and provides the inverted CM voltage signal back to the non-inverting input and the inverting input of the transconductor for enabling the CM suppression.

Methods and devices for a cascode differential input pair with low headroom voltage and high output impedance are presented. The cascode differential input pair includes first and second input (cascode) stages, each including a common-source regular transistor in series connection with a common-gate intrinsic transistor. Sources of the regular transistors are tied, and gates of the intrinsic transistors are tied. A gate voltage to the intrinsic transistors is provided by a source voltage at the sources of the regular transistors, the source voltage based on a common mode input voltage of the cascode differential input pair. According to one aspect, the cascode differential input pair is part of a differential amplifier that includes a current source coupled to the sources of the regular transistors, and a load coupled to drains of the intrinsic transistors.