Apparatus and associated methods relate to generating a programmable differential threshold with a common mode signal derived from a received signal, and comparing a differential component of the received signal to the programmable differential threshold signal to improve signal loss detection accuracy in the presence of noise. In an illustrative example, the comparison may be performed in a signal loss detection circuit. The signal loss detection circuit may, for example, process a received input signal in an independent path in parallel with a main signal path. The programmable differential threshold may be set to a predetermined level as a function of an acceptable noise level. Based on the comparison, some implementations may advantageously respond to received signal loss, which may result from, for example, a signal path interruption.

This application relates to driver circuitry (200) for receiving a digital input signal (D) and outputting, at first and second output nodes (203p, 203n), first and second analogue driving signals respectively for driving a transducer (101), e.g. loudspeaker, in a bridge-tied-load configuration. The driver circuitry may particularly be suitable for driving low-impedance transducers. The driver circuitry has first and second digital-to-analogue converters (201p, 201n) configured to receive the digital input signal and the outputs of the first and second digital-to-analogue converters are coupled to the first and second output nodes respectively. A differential-output amplifier circuit (202) has outputs connected to the first and second output nodes and is configured to regulate the outputs of the digital-to-analogue converters at output nodes to provide the analogue driving signals.

An automatic gain control circuit includes a linear-to-log conversion circuit, a current amplifier circuit, and an amplitude sense circuit. The current amplifier circuit includes a current input terminal coupled to an output terminal of the linear-to-log conversion circuit. The amplitude sense circuit includes an input terminal coupled to an output terminal of the current amplifier circuit, and an output terminal coupled to a gain control input terminal of the current amplifier circuit.

An operational amplifier includes a single-stage amplifier and a current controller. The single-stage amplifier receives an input signal, and amplifies the input signal to generate an output signal, wherein the single-stage amplifier includes a voltage controlled current source circuit that operates in response to a bias voltage input. The current controller receives the input signal, and generates the bias voltage input according to the input signal.

A magnetic operational amplifier having a differential stage includes a first magnetic field effect transistor MAGFET and a differential signal conditioner, the differential signal conditioner including a load stage, a differential input pair connected to the load stage and a biasing current source connected to the differential input pair; the magnetic field effect transistor MAGFET being connected to the load stage as a second differential input pair and the differential signal conditioner including a second biasing current source connected to the magnetic field effect transistor MAGFET.

An operational amplifier includes: a first amplifier stage, configured to generate first output voltages according to first input voltages; a second amplifier stage, configured to generate second output voltages according to the first output voltages; a second output stage circuit, configured to replicate an equivalent or a scaled-down version of the first output stage circuit; a first common-mode feedback circuit, configured to keep an output common-mode voltage of the second output stage circuit at a predetermined value; a logic loop circuit configured to, when the operational amplifier operates in a direct current calibration phase, adjust a difference between the first output voltages; a bias circuit, configured to generate a voltage close to a common-mode voltage of the first output voltages produced after the operational amplifier is turned on, the voltage serving as a reference voltage of a second common-mode feedback circuit.

An amplifier arrangement has a first differential stage with a first transistor pair, a second differential stage with a first and a second transistor pair, each pair having a common source connection. The amplifier arrangement further has a first complementary differential stage with a transistor pair having opposite conductivity type, and a second complementary differential stage with a first and a second transistor pair of the complementary conductivity type. The first and the second complementary differential stage are connected symmetrically compared to the first and the second differential stage. The transistors of the second differential stage and the second complementary differential stage are symmetrically connected to form respective first, second, third and fourth current paths. A pair of output terminals is coupled to the first and the fourth current path. Gate terminals of the transistors are coupled to a respective pair of input terminals.

An operational amplifier includes: a first amplifier stage, configured to generate first output voltages according to first input voltages; a second amplifier stage, configured to generate second output voltages according to the first output voltages; a second output stage circuit, configured to replicate an equivalent or a scaled-down version of the first output stage circuit; a first common-mode feedback circuit, configured to keep an output common-mode voltage of the second output stage circuit at a predetermined value; a logic loop circuit configured to, when the operational amplifier operates in a direct current calibration phase, adjust a difference between the first output voltages; a bias circuit, configured to generate a voltage close to a common mode voltage of the first output voltages produced after the operational amplifier is turned on, the voltage serving as a reference voltage of a second common-mode feedback circuit.

A differential amplifier circuit comprises: first and second input terminals; first and second output terminals; a first transistor comprising a gate terminal connected to the first input terminal; a second transistor comprising a gate terminal connected to the second input terminal; a first resistor connected between the source terminal of the first transistor and the source terminal of the second transistor; a third transistor comprising a drain terminal connected to the source terminal of the first transistor, a gate terminal connected to the drain terminal of the first transistor, and a source terminal connected to the first output terminal; a fourth transistor comprising a drain terminal connected to the source terminal of the second transistor, a gate terminal connected to the drain terminal of the second transistor, and a source terminal connected to the second output terminal; first to fourth current sources; and second and third resistors.

A chopper amplifying circuit employing a negative impedance compensation technique, including a differential input end, a first-level chopper switch, a first-level amplifying circuit, a second-level chopper switch, a second-level amplifying circuit, a negative impedance converting circuit, a negative feedback unit, an input capacitor, and a differential output end, is provided. The differential input end is connected to the first-level chopper switch. An output terminal of the first-level chopper switch is connected to the first-level amplifying circuit through the input capacitor. The first-level amplifying circuit is connected to the second-level chopper switch, which is connected to the second-level amplifying circuit. The second-level amplifying circuit is connected to the differential output end, and is also connected to a feedback input end of the first-level amplifying circuit through the negative feedback unit. The negative impedance converting circuit is parallel-connected to a signal input end of the first-level amplifying circuit.