Embodiments of a passive buffer circuit and a wideband communication circuit that uses the passive buffer circuit are disclosed. In an embodiment, the passive buffer circuit includes buffer elements connected between input terminals and output terminals that are connected to input terminals of a communication component circuit with a plurality of input transistors. Each of the buffer elements provides a first path with a resistor and a second path with a series-connected capacitor and inductor. The passive buffer circuit further includes current sources connected between the output terminals and at least one fixed voltage and a feedback loop from the input transistors to the current sources to control direct current (DC) voltage at each of the input terminals of the communication component circuit. The feedback loop includes an error amplifier that controls the current sources based on voltages on the input transistors with respect to a reference voltage.

A reference voltage generation circuit may include: a first reference current path formed through a first node and a first transistor; a second reference current path formed through a second node and a second transistor; a first feedback loop configured to feed a first current back to the first and second reference current paths such that voltage levels of the first and second nodes are kept the same; and a second feedback loop configured to control the currents flowing through the first and second transistors according to a second current.

This description relates, generally, to protecting a circuit from an input voltage. Various examples include an apparatus including one or more circuits to draw current from, or provide current to, a pair of connectors for an input circuit. The connectors may be for electrical coupling to first and second terminals of a twisted pair. The one or more circuits may be at least partially responsive to positive and negative biasing signals. The apparatus may additionally include an operational amplifier to generate the positive and negative biasing signals. The operational amplifier may include: a first input terminal at least partially responsive to a reference voltage and a second input terminal at least partially responsive to a common-mode voltage of the input circuit. Related systems and methods are also disclosed.

An analog front-end receiver including a termination resistor configured to receive first and second differential signals from different data lines, the second differential signal being differential with respect to the first differential signal, an active equalizer configured to receive a first input differential signal through a first input node and a second input differential signal through a second input node, the first and second input differential signals both having an input common mode voltage, the first and second input differential signals being based on the first and second differential signal, respectively, and output first and output differential signals to first and second output nodes, respectfully, the second output differential signal being differential with respect to the first output differential signal, and an input common mode voltage generator configured to adjust the input common mode voltage to be equal to an output common mode voltage of the first output differential signal.

An amplifier circuit has: a first amplifier circuit, including a chopper circuit amplifying a first differential signal input between first and second input terminals to output a second differential signal; and a second amplifier circuit amplifying the second differential signal to output a single-ended signal. The second amplifier circuit includes: a first circuit including first and second transistors, the first circuit being connected to the first amplifier circuit so that the second differential signal input into gates of these transistors, the first circuit converting the second differential signal to a current flowing into a first node connected to the first transistor and a current flowing into a second node connected to the second transistor; and a second circuit negatively feeding back a voltage at the second node so that the difference in voltage between these nodes is reduced. The second amplifier circuit outputs the single-ended signal from the first node.

A system, disposed within a wearable hearing device, includes a sound producing device (SPD) driven by a driving voltage, a first sound sensing device, and a subtraction circuit. The first sound sensing device is configured to sense a combined sound pressure produced at least by the SPD and generate a sensed signal accordingly. The subtraction circuit has a first input terminal, a second input terminal, and a first output terminal. The first input terminal is coupled to the first sound sensing device, and the first output terminal is coupled to the SPD. A first phase delay between the driving voltage and the sensed signal is less than 60°.

A system may include a front end differential amplifier having two input terminals, two input resistors, each of the two input resistors coupled to a respective one of the two input terminals, and an input common mode biasing circuit for an output stage of the front end differential amplifier, the input common mode biasing circuit comprising two current sources configured to generate currents for biasing the output stage of the front end differential amplifier.

An operational amplifier with one or more fully-differential amplifier stages has a common-mode control input. A low-frequency feedback control path is coupled between an output of the fully-differential amplifier stages and the common-mode control input to control low-frequency drift of the common-mode voltage of the output of the stages. A high-frequency feed-forward control path couples a pair of inputs of the stages to control high-frequency ripple of a common-mode voltage of the inputs of the stages. One or more of the differential amplifier stages may have a bias input that controls a direct-current (DC) bias voltage of gates of pull-up transistors of the stage that is both DC and capacitively coupled to the gates so that the stage operates with class A bias at DC and with class AB bias at high frequencies.

An analog front-end receiver including a termination resistor configured to receive first and second differential signals from different data lines, the second differential signal being differential with respect to the first differential signal, an active equalizer configured to receive a first input differential signal through a first input node and a second input differential signal through a second input node, the first and second input differential signals both having an input common mode voltage, the first and second input differential signals being based on the first and second differential signal, respectively, and output first and output differential signals to first and second output nodes, respectfully, the second output differential signal being differential with respect to the first output differential signal, and an input common mode voltage generator configured to adjust the input common mode voltage to be equal to an output common mode voltage of the first output differential signal.

Aspects of the disclosure provide for a method. In at least some examples, the method includes receiving, at a circuit, data via a differential input signal. The method further includes detecting a falling edge in the data received via the differential input signal. The method further includes holding an output of the circuit at a final logical value of the data. The method further includes disabling a transmitter of the circuit while holding the output of the circuit at the final logical value of the data. The method further includes releasing the output of the circuit from the final logical value of the data.