A bias circuit for a bipolar RF amplifier is described. The bias circuit includes a current source coupled to a bias network. The bias network supplies a base current to the transistors in the amplifier circuit of the bipolar RF amplifier. The bias circuit includes a buffer coupled to the bias network and to the bipolar RF amplifier. The buffer provides additional base current to the amplifier circuit of bipolar RF amplifier and sinks avalanche current generated by the amplifier circuit of the bipolar RF amplifier.

An amplifier circuit includes a first transistor; a first resistor to which a first potential is applied, the first resistor being connected to an emitter of the first transistor; a second resistor to which a second potential is applied, the second resistor being connected to a collector of the first transistor; and a signal control circuit configured to apply, to a base of the first transistor, a voltage that has been level-shifted based on an average value of a voltage at the collector of the first transistor, the signal control circuit being provided between the collector and the base of the first transistor.

Design of ultra broadband transimpedance amplifiers (TIA) for optical fiber communications is disclosed. In one embodiment, a TIA comprises a g.sub.m-boosted dual-feedback common-base stage, a level shifter and an RC-degenerated common-emitter stage, and a first emitter-follower stage, wherein the first emitter follower stage is inductively degenerated. An output of the TIA is buffered using a second emitter-follower stage.

Logarithmic current-to-voltage converters with emitter resistance compensation are disclosed herein. In certain embodiments, a logarithmic current-to-voltage converter includes a logarithmic bipolar transistor that converts an input current to a logarithmic voltage, and an emitter resistance compensation circuit that includes a replica of the logarithmic bipolar transistor. The emitter resistance compensation circuit processes a copy of the input current to generate an emitter resistance compensation signal that adjusts the logarithmic voltage to correct for an error introduced by an emitter resistance of the logarithmic bipolar transistor. By providing emitter resistance compensation in this matter, logarithmic current-to-voltage conversion with high accuracy and low log error is achieved.

A semiconductor substrate includes emitter electrodes for multiple high-frequency amplifying transistors. An insulating substrate includes multiple land electrodes, ground electrodes, and multiple inductor electrodes. The land electrodes are formed on the front surface or near the front surface of the insulating substrate, and are joined to the respective emitter electrodes. The ground electrodes are formed inside the insulating substrate. Each of the inductor electrodes couples a corresponding one of the land electrodes to any of the ground electrodes in such a manner that the lengths of the coupling to the ground electrodes are individually determined.

An amplifier circuit includes an input amplifier; an output unity gain buffer; and a second unity gain buffer. The output unity gain buffer and the second unity gain buffer are each configured to receive a signal from an input amplifier. The output unity gain buffer is configured to provide an output voltage to an amplifier output, and the second unity gain buffer is configured to provide a bootstrap signal to the input amplifier. A unity gain amplifier includes an input unity gain amplifier; and an output unity gain buffer and a second unity gain buffer. The buffers are configured to receive a signal from an input amplifier. The output unity gain buffer is configured to provide an output voltage to an amplifier output, and the second unity gain buffer is configured to provide a bootstrap signal to the input unity gain amplifier.

A high-speed low-noise trans-impedance amplifier (TIA) with fast overdrive recovery is suitable for use in light detection and ranging (LIDAR) receivers.

An amplifier circuit includes a first transistor; a first resistor to which a first potential is applied, the first resistor being connected to an emitter of the first transistor; a second resistor to which a second potential is applied, the second resistor being connected to a collector of the first transistor; and a signal control circuit configured to apply, to a base of the first transistor, a voltage that has been level-shifted based on an average value of a voltage at the collector of the first transistor, the signal control circuit being provided between the collector and the base of the first transistor.

Design of ultra broadband transimpedance amplifiers (TIA) for optical fiber communications is disclosed. In one embodiment, a TIA comprises a g.sub.m-boosted dual-feedback common-base stage, a level shifter and an RC-degenerated common-emitter stage, and a first emitter-follower stage, wherein the first emitter follower stage is inductively degenerated. An output of the TIA is buffered using a second emitter-follower stage.

A semiconductor substrate includes emitter electrodes for multiple high-frequency amplifying transistors. An insulating substrate includes multiple land electrodes, ground electrodes, and multiple inductor electrodes. The land electrodes are formed on the front surface or near the front surface of the insulating substrate, and are joined to the respective emitter electrodes. The ground electrodes are formed inside the insulating substrate. Each of the inductor electrodes couples a corresponding one of the land electrodes to any of the ground electrodes in such a manner that the lengths of the coupling to the ground electrodes are individually determined.