Disclosed is a differential voltage supplying apparatus configured to supply, to a neural activity recorder, an input signal generated by combining, with a direct current (DC) power supply, a common-mode signal determined from a voltage applied to a detection electrode and a reference electrode connected to the neural activity recorder, and improve a common-mode rejection ratio of the neural activity recorder and generate a DC power supply.

Disclosed is a differential voltage supplying apparatus configured to supply, to a neural activity recorder, an input signal generated by combining, with a direct current (DC) power supply, a common-mode signal determined from a voltage applied to a detection electrode and a reference electrode connected to the neural activity recorder, and improve a common-mode rejection ratio of the neural activity recorder and generate a DC power supply.

A transconductance circuit has an input terminal (V.sub.IN) and an output terminal (Out), a first current source (4) having a gate connected to said input terminal (V.sub.IN); and a second current source (5), in parallel with said first current source, and having a higher transconductance and a wider dynamic range than the first current source. The current sources are configured so that at a low input voltage only the first current source (4) is on. A voltage drop circuit provides a lower bias voltage for the second current source than for the first current source.

A transconductance circuit has an input terminal (V.sub.IN) and an output terminal (Out), a first current source (4) having a gate connected to said input terminal (V.sub.IN); and a second current source (5), in parallel with said first current source, and having a higher transconductance and a wider dynamic range than the first current source. The current sources are configured so that at a low input voltage only the first current source (4) is on. A voltage drop circuit provides a lower bias voltage for the second current source than for the first current source.

An output circuit (10) according to the present invention includes a first output terminal (VO) and a second output terminal (SGND); an output transistor (MP1) connected between a first fixed-potential node (VCC) and the first output terminal; an output load (15) connected between the first output terminal and the second output terminal; a control circuit (13) that controls the output transistor so that a monitor voltage (VS) based on a voltage between the first output terminal and the second output terminal matches an input voltage (VI); a constant voltage source (16) whose one end is connected to the second terminal and whose other end is connected to a second fixed-potential node (GND); and a circuit (R4) that forms a current path between the first output terminal and the second fixed-potential node. Accordingly, in the output circuit, stability of a negative feedback loop can be enhanced, and linearity of an output voltage with respect to an input voltage can be enhanced.

An output circuit (10) according to the present invention includes a first output terminal (VO) and a second output terminal (SGND); an output transistor (MP1) connected between a first fixed-potential node (VCC) and the first output terminal; an output load (15) connected between the first output terminal and the second output terminal; a control circuit (13) that controls the output transistor so that a monitor voltage (VS) based on a voltage between the first output terminal and the second output terminal matches an input voltage (VI); a constant voltage source (16) whose one end is connected to the second terminal and whose other end is connected to a second fixed-potential node (GND); and a circuit (R4) that forms a current path between the first output terminal and the second fixed-potential node. Accordingly, in the output circuit, stability of a negative feedback loop can be enhanced, and linearity of an output voltage with respect to an input voltage can be enhanced.

A biasing device for direct current (DC) biasing a linear power amplifier that comprises multiple linear power amplifier circuits that are ideally identical to each other; wherein the biasing device may include a replica circuit that is a replica of a linear power amplifier circuit of the multiple linear power amplifier circuits; and a bias control circuit; wherein the bias control circuit is configured to feed the replica circuit with one or more DC biasing signals thereby maintaining at a constant value a replica DC current that is consumed by the replica circuit, and maintaining at a fixed value a replica DC voltage of a replica output node of the replica circuit; and wherein the replica circuit is coupled the multiple linear power amplifier circuits and is configured to supply DC voltage bias signals that force each linear power amplifier circuit of the multiple linear power amplifier circuits to consume a linear power amplifier circuit DC current that equals the replica DC current, when the linear power amplifier circuit is fed with a linear power amplifier DC voltage that either equals the replica DC voltage or differs from the replica DC voltage by a fraction of the replica DC voltage.

A biasing device for direct current (DC) biasing a linear power amplifier that comprises multiple linear power amplifier circuits that are ideally identical to each other; wherein the biasing device may include a replica circuit that is a replica of a linear power amplifier circuit of the multiple linear power amplifier circuits; and a bias control circuit; wherein the bias control circuit is configured to feed the replica circuit with one or more DC biasing signals thereby maintaining at a constant value a replica DC current that is consumed by the replica circuit, and maintaining at a fixed value a replica DC voltage of a replica output node of the replica circuit; and wherein the replica circuit is coupled the multiple linear power amplifier circuits and is configured to supply DC voltage bias signals that force each linear power amplifier circuit of the multiple linear power amplifier circuits to consume a linear power amplifier circuit DC current that equals the replica DC current, when the linear power amplifier circuit is fed with a linear power amplifier DC voltage that either equals the replica DC voltage or differs from the replica DC voltage by a fraction of the replica DC voltage.

A low-dropout voltage regulator (2) comprises: a differential amplifier portion (4) including a first amplifier input connected to a reference voltage (16), a second amplifier input, and a differential output which is determined by a difference between the reference voltage and a voltage on the second amplifier input; an output portion (10) arranged to provide a regulator output voltage (62) which is controlled by the differential output of the amplifier portion, the second amplifier input being connected to or derived from (70) the regulator output voltage; and a biasing portion (8) arranged to measure an external load current and to provide a biasing current to the differential amplifier portion which depends on the load current.

A low-dropout voltage regulator (2) comprises: a differential amplifier portion (4) including a first amplifier input connected to a reference voltage (16), a second amplifier input, and a differential output which is determined by a difference between the reference voltage and a voltage on the second amplifier input; an output portion (10) arranged to provide a regulator output voltage (62) which is controlled by the differential output of the amplifier portion, the second amplifier input being connected to or derived from (70) the regulator output voltage; and a biasing portion (8) arranged to measure an external load current and to provide a biasing current to the differential amplifier portion which depends on the load current.