A variable-gain amplifier includes two amplification and attenuation branches, and first and a second resistive elements that are coupled between the two branches. Each branch includes a voltage follower stage and a configurable amplification stage. The voltage follower stages are intended to receive a differential signal and are configured to deliver, via the first resistive element, an intermediate differential current signal. The amplification stages are intended to receive the intermediate differential current signal and a digital control word, and are configured to deliver, via the second resistive element, an output differential voltage signal depending on the value of the digital control word.

A differential amplifier is provided. The differential amplifier includes: a differential input circuit, adjusting a second current and a third current flowing into the differential input circuit according to a first input voltage, a second input voltage, and a first current; a first current source circuit, generating the first current according to a first reference voltage; a current-mirror circuit, generating a fifth current according to a fourth current; a second current source circuit, generating a sixth current and a seventh current according to a second reference voltage; and an impedance circuit, coupled to the current-mirror circuit and a ground terminal, the differential amplifier having a low output voltage error.

A differential amplifier is provided. The differential amplifier includes: a differential input circuit, adjusting a second current and a third current flowing into the differential input circuit according to a first input voltage, a second input voltage, and a first current; a first current source circuit, generating the first current according to a first reference voltage; a current-mirror circuit, generating a fifth current according to a fourth current; a second current source circuit, generating a sixth current and a seventh current according to a second reference voltage; and an impedance circuit, coupled to the current-mirror circuit and a ground terminal, the differential amplifier having a low output voltage error.

A negative impedance circuit includes: a differential circuit stage; a positive feedback path from an output of the differential circuit stage to a first input of the differential circuit stage; and a negative feedback path from the output of the differential circuit stage to a second input of the differential circuit stage. The negative feedback path includes a first transistor, and a unitary gain path from the output of the differential circuit stage to the second input of the differential circuit stage, the unitary gain path coupled to ground via a reference impedance. The positive feedback path includes a second transistor. The first and second transistors are coupled in a current mirror arrangement and have respective control electrodes configured to be driven by the output of the differential circuit stage, where the negative impedance circuit causes a negative impedance at the first input of the differential circuit stage.

A variable-gain amplifier includes two amplification and attenuation branches, and first and a second resistive elements that are coupled between the two branches. Each branch includes a voltage follower stage and a configurable amplification stage. The voltage follower stages are intended to receive a differential signal and are configured to deliver, via the first resistive element, an intermediate differential current signal. The amplification stages are intended to receive the intermediate differential current signal and a digital control word, and are configured to deliver, via the second resistive element, an output differential voltage signal depending on the value of the digital control word.

Disclosed is an amplifier capable of minimizing shortcircuit current of an output stage of a buffer upon transition of an output voltage while having a high slew rate without increasing power consumption. The amplifier includes an input unit, a conversion unit, an amplification unit, a frequency compensation circuit, and a short-circuit current minimization circuit. Alternatively, the amplifier includes an input unit, a conversion unit, an amplification unit, a frequency compensation circuit, a short-circuit current minimization circuit, and a slew rate improvement circuit.

An example apparatus includes a first transistor coupled between a supply node and a first node, a current mirror having a first side and a second side, and a second transistor coupled between the first node and the first side of the current mirror. The input buffer further includes a third transistor coupled between the first node and the second side of the current mirror, and a first capacitor coupled between a source and a drain of the second transistor.

A differential pair gain stage is disclosed. In one embodiment, the gain stage includes a differential pair of depletion-mode transistors, including a first and a second n-type transistor. In certain embodiments of the invention, the depletion mode transistor may be GaN (gallium nitride) field effect transistors. The gain stage includes an active load including one or more depletion mode transistors electrically coupled to at least one of the drains of depletion mode transistors of the differential pair. The active load may include a source follower for maintaining the AC voltages at the drains of the differential pair at a constant value and may further include a casocde stage for setting a fixed drain source voltage across the output transistors to increase the output impedance and gain of the stage.

Embodiments describe a transadmittance amplifier comprising an inverting output port and a non-inverting output port. The transadmittance amplifier comprising a first differential transistor pair having a first transistor comprising an inverting input port. The first transistor is configured to provide an output current to the inverting output port. A second transistor comprising a non-inverting input port. The second transistor is configured to provide an output current to the non-inverting output port. A second differential transistor pair having a third transistor comprising an inverting input port and a fourth transistor comprising a non-inverting input port. A first current source and a second current source. The transadmittance amplifier comprises a first current mirror which is configured to mirror an output current of the fourth transistor to the inverting output port and a second current mirror which is configured to mirror an output current of the third transistor to the non-inverting output port.

Embodiments describe a transadmittance amplifier comprising an inverting output port and a non-inverting output port. The transadmittance amplifier comprising a first differential transistor pair having a first transistor comprising an inverting input port. The first transistor is configured to provide an output current to the inverting output port. A second transistor comprising a non-inverting input port. The second transistor is configured to provide an output current to the non-inverting output port. A second differential transistor pair having a third transistor comprising an inverting input port and a fourth transistor comprising a non-inverting input port. A first current source and a second current source. The transadmittance amplifier comprises a first current mirror which is configured to mirror an output current of the fourth transistor to the inverting output port and a second current mirror which is configured to mirror an output current of the third transistor to the non-inverting output port.