A chopper-stabilized amplifier that includes an analog driven level shifter is disclosed. The analog driven level shifter changes the levels of a pair of complementary clock signals according to a level associated with an input signal to the chopper-stabilized amplifier. The level shifted complementary clock signals are used to control switching devices used for chopping input signals of various voltages. The chopper-stabilized amplifier also includes symmetrical passive RC notch filters having two cut-off frequencies to reduce ripple noise from the chopping.

In accordance with an embodiment, a circuit includes: a first super source follower; a compensation circuit having a compensating node configured to provide a voltage of opposite phase of a voltage of an internal node of the first super source follower; and a first compensation capacitor coupled between an input of the first super source follower and the compensating node of the compensation circuit.

Provided is a condenser microphone circuit that can support variation in power supply voltage of a phantom power supply using a wiring system of two lines. A condenser microphone circuit includes a microphone unit, an FET, a constant current diode, a collector grounding first transistor that generates an operation power supply of the FET, a first resistor that sets base potential of the first transistor, a collector grounding second transistor that amplifies an output signal from the FET, a second resistor that sets base potential of the second transistor, and an output circuit. A base of the first transistor is connected to a source of the FET, an emitter of the first transistor is connected to a drain of the FET, a base of the second transistor is connected to the drain of the FET, an emitter of the second transistor is connected to the output circuit, and the second resistor divides voltage on a cathode side of the constant current diode.

A chopper-stabilized amplifier that includes an analog driven level shifter is disclosed. The analog driven level shifter changes the levels of a pair of complementary clock signals according to a level associated with an input signal to the chopper-stabilized amplifier. The level shifted complementary clock signals are used to control switching devices used for chopping input signals of various voltages. The chopper-stabilized amplifier also includes symmetrical passive RC notch filters having two cut-off frequencies to reduce ripple noise from the chopping.

A line receiver comprising a switched capacitor circuit and a buffer is described. The buffer may be configured to receive, through the switched capacitor circuit, an analog signal. In response, the buffer may provide an output signal to a load, such as an analog-to-digital converter. The switched capacitor circuit may be controlled by a control circuitry, and may charge at least one capacitive element to a desired reference voltage. The reference voltage may be selected so as to bias the buffer with a desired DC current, and consequently, to provide a desired degree if linearity. The line receiver may further comprise a bias circuit configured to generate the reference voltage needed to bias the buffer with the desired DC current.

An amplifier that amplifies a differential signal includes first and second input terminals for receiving two input signals; first and second diodes each including an anode and a cathode, the anodes being electrically connected to the first and second input terminals; first and second bias current sources being respectively electrically connected to the cathodes of the first and second diodes; an operational amplifier connected to the cathode of the first diode and the cathode of the second diode and configured to amplify a differential signal between signals generated at the cathodes of the first and second diodes; a capacitive element being electrically connected between an input and an output of the operational amplifier; and a differential amplifier provided between the operational amplifier and the first and second input terminals and configured to amplify the two input signals. The first and second bias current sources include a current mirror circuit.

An amplifier that amplifies a differential signal includes first and second input terminals for receiving two input signals; first and second diodes each including an anode and a cathode, the anodes being electrically connected to the first and second input terminals; first and second bias current sources being respectively electrically connected to the cathodes of the first and second diodes; an operational amplifier connected to the cathode of the first diode and the cathode of the second diode and configured to amplify a differential signal between signals generated at the cathodes of the first and second diodes; a capacitive element being electrically connected between an input and an output of the operational amplifier; and a differential amplifier provided between the operational amplifier and the first and second input terminals and configured to amplify the two input signals. The first and second bias current sources include a current mirror circuit.

An embodiment amplifier circuit includes a pair of subcircuits that includes a first subcircuit and a second subcircuit, each of which includes a buffer amplifier and a feedback circuit that includes a feedback capacitor. The amplifier circuit also includes a pair of output terminals. The first subcircuit and the second subcircuit each generate a different output signal of a pair of output signals that includes a first output signal and a second output signal. The amplifier circuit is configured for receiving a positive differential input signal at the first subcircuit, receiving a negative differential input signal at the second subcircuit, and receiving the pair of output signals at the pair of output terminals. The amplifier circuit is also configured for transmitting the first output signal to the feedback circuit of the first subcircuit, and transmitting the second output signal to the feedback circuit of the second subcircuit.

An apparatus, such as a coherent optical receiver, includes a transimpedance amplifier (TIA) with differential outputs, and a multi-tanh type current limiter connected across the differential outputs of the transimpedance amplifier. The multi-tanh type current limiter includes two tanh-type current limiters shifted in voltage and connected to subtract an output current thereof from an output current of the TIA.

An apparatus, such as a coherent optical receiver, includes a TIA, the TIA including a cascode circuit having a cascode node. A first tunable element is connected to tunably shunt the cascode node to vary a voltage gain of the TIA, e.g., up to a first amount. Implementations of the TIA further include another tunable element connected to vary a load of the cascode circuit to vary the voltage gain, e.g., up to a second amount. A current steering circuit may be provided to vary the voltage gain up to a third amount, each of the amounts being only a fraction of a target voltage gain variation of the TIA.