Nordic Semiconductor Asa

Dominik Przyborowski

A common-mode feedback circuit for a fully differential amplifier comprises first (M), second (M), and third (M) transistors, each having a respective drain, source, gate, and back-gate terminals. The drain terminal of the first transistor (M) and the gate terminals of the first, second, and third transistors (M, M, M) are connected together at a bias current terminal. The drain terminals of the second and third transistors are connected together at a tail current terminal. The source terminals of the first, second, and third transistors are connected together. The back-gate terminal of the first transistor (M) is arranged to receive a common-mode reference voltage input (V), the back-gate terminal of the second transistor (M) is arranged to receive a positive output voltage (V) from the fully differential amplifier, and the back-gate terminal of the third transistor (M) is arranged to receive a negative output voltage (V) from the fully differential amplifier.

Common-mode feedback

A start-up circuit for a self-biasing generator provides a reference voltage or a reference current, the start-up circuit including an impedance circuit. In response to a start-up signal input to the start-up circuit, the impedance circuit is coupled to a bias voltage line of a current mirror circuit of the self-biasing generator, thereby inducing current to flow in the self-biasing generator and starting the self-biasing generator. A bypass current source is coupled to the current mirror circuit and to the impedance. The bypass current source is configured to be driven by a current in the current mirror circuit and to supply current to the impedance in proportion to the current in the current mirror circuit, thereby limiting the current induced to the self-biasing generator by the start-up circuit.

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Trondheim, Norway

Dominik Przyborowski