A transimpedance amplifier circuit (1) includes an amplifier (22) that amplifies a received signal, an automatic gain control (AGC) circuit (2) that controls the amplification gain of the amplifier by a first time constant in accordance with the level of the received signal, and a first selection circuit (25) that selects the first time constant from a plurality of predetermined values. This can simultaneously implement a short time constant of an AGC function necessary to instantaneously respond to a burst signal and a long time constant of the AGC function necessary to obtain a satisfactory bit error rate (BER) characteristic in a continuous signal by an inexpensive and compact circuit arrangement.

A differential amplifying apparatus includes an input matching circuit serving as an input balun to which a signal inputted to an input terminal is input, an output matching circuit serving as an output balun that outputs a signal to an output terminal, first and second amplifiers provided in parallel between the input balun and the output balun and configured to output a differential signal, a diode provided between a reference potential and a path between the input balun and the first amplifier, a second diode provided between a reference potential and a path between the input balun and the second amplifier, and a bias circuit that applies a bias to the first diode and the second diode, in which a cathode of the first diode and a cathode of the second diode are connected to the reference potential side.

An offset cancellation circuit and method are provided where successive stages of cascaded amplifiers are operated in a saturated state. Biasing is provided, by a feedback amplifier, connected in a feedback loop for each cascaded amplifier, so as to be responsive, in a non-saturated state, to the input of an associated amplifier stage operating in the saturated state.

An offset cancellation circuit and method are provided where successive stages of cascaded amplifiers are operated in a saturated state. Biasing is provided, by a feedback amplifier, connected in a feedback loop for each cascaded amplifier, so as to be responsive, in a non-saturated state, to the input of an associated amplifier stage operating in the saturated state.

A transimpedance amplifier includes a first and a second power supply terminal for receiving a positive constant supply voltage, wherein the second power supply terminal represents a ground, and an input terminal adapted to be connected to a current source. The transimpedance amplifier further comprises a transistor comprising a control terminal and two further terminals, wherein the input terminal is connected to the control terminal of the first transistor. An inductor is connected between the first of the two further terminals of the transistor and the first power supply terminal, and a bias network is connected between the second of the two further terminals of the transistor and ground. Specifically, the transimpedance amplifier is configured such that the resistance between said first of said two further terminals of said first transistor and said first power supply terminal is small enough, such that said transimpedance amplifier operates as a differentiator.

A transimpedance amplifier includes a first and a second power supply terminal for receiving a positive constant supply voltage, wherein the second power supply terminal represents a ground, and an input terminal adapted to be connected to a current source. The transimpedance amplifier further comprises a transistor comprising a control terminal and two further terminals, wherein the input terminal is connected to the control terminal of the first transistor. An inductor is connected between the first of the two further terminals of the transistor and the first power supply terminal, and a bias network is connected between the second of the two further terminals of the transistor and ground. Specifically, the transimpedance amplifier is configured such that the resistance between said first of said two further terminals of said first transistor and said first power supply terminal is small enough, such that said transimpedance amplifier operates as a differentiator.