A method and circuit are provided for implementing enhanced CMOS inverter based optical Transimpedance Amplifiers (TIAs). A transimpedence amplifer (TIA) includes a photo-detector, and the TIA is formed by a first TIA inverter and a second TIA inverter. The first TIA inverter has an input from a cathode side of the photo-detector and the second inverter has an input from an anode side of the photo-detector. A replica TIA is formed by two replica inverters, coupled to a respective input to a first operational amplifier and a second operational amplifier. The first operational amplifier and the second operational amplifier have a feedback configuration for respectively regulating a set voltage level at the cathode side of the photo-detector input of the first inverter and at the anode side of the photo-detector input of the second inverter.

In some implementations, an automatic gain control (AGC) circuit comprises: a pre-divider circuit operable to pre-divide an input signal according to a pre-divider circuit setting and output a pre-divided signal; a pre-amplifier operable to pre-amplify the pre-divided signal and output a pre-amplified signal; a post-divider circuit operable to post-divide the pre-amplified signal according to a post-divider circuit setting; an analog-to-digital converter (ADC) operable to generate a digital data stream from the post-divided signal; logic operable to sample the digital data stream; determine a pre-divider circuit setting and a post-divider circuit setting based on the sampled data stream; set the pre-divider circuit and the post-divider circuit based on the determined settings; and generate a received signal strength value based on the pre-divider circuit setting and the post-divider circuit setting.

A burst-mode TIA circuit for use in PON receivers is provided that supports multiple data rates, has high receiver sensitivity, wide dynamic range, and that performs burst-mode synchronization very quickly. The multi-rate burst-mode TIA circuit has a high-speed data path that has low input-referred noise. Based on the chosen data rate at which the multi-rate burst-mode TIA circuit will operate, the rate select switch selects an appropriate feedback resistor of the resistive feedback network.

Some embodiments described herein are directed to a photo sensor and a method of operating a photo sensor. In an embodiment, a photo sensor comprises a photo diode, a filter circuit, and an output circuit. The filter circuit has an input node configured to be electrically coupled to an output node of the photo diode, and has an output node. The filter circuit has an adjustable gain, and the adjustable gain is adjustable based on a signal output from the filter circuit. The output circuit has an input node configured to be electrically coupled to the output node of the filter circuit.

Some embodiments described herein are directed to a photo sensor and a method of operating a photo sensor. In an embodiment, a photo sensor comprises a photo diode, a filter circuit, and an output circuit. The filter circuit has an input node configured to be electrically coupled to an output node of the photo diode, and has an output node. The filter circuit has an adjustable gain, and the adjustable gain is adjustable based on a signal output from the filter circuit. The output circuit has an input node configured to be electrically coupled to the output node of the filter circuit.

An apparatus is described which uses directly modulated InGaN Light-Emitting Diodes (LEDs) or InGaN lasers as the transmitters for an underwater data-communication device. The receiver uses automatic gain control to facilitate performance of the apparatus over a wide-range of distances and water turbidities.

A burst-mode TIA circuit for use in PON receivers is provided that supports multiple data rates, has high receiver sensitivity, wide dynamic range, and that performs burst-mode synchronization very quickly. The multi-rate burst-mode TIA circuit has a high-speed data path that has low input-referred noise. Based on the chosen data rate at which the multi-rate burst-mode TIA circuit will operate, the rate select switch selects an appropriate feedback resistor of the resistive feedback network.

Methods and systems for accurate gain adjustment of a transimpedance amplifier using a dual replica and servo loop is disclosed and may include, in a transimpedance amplifier (TIA) circuit comprising a first TIA, a second TIA, and a third TIA, each comprising a configurable feedback impedance, and a control loop, where the control loop comprises a gain stage with inputs coupled to outputs of the first and second TIAs and an output coupled to the configurable feedback impedance of the second and third TIAs: configuring a gain level of the first TIA by configuring its feedback impedance, configuring a gain level of the third TIA by configuring a reference current applied to an input of the first TIA, and amplifying a received electrical signal to generate an output voltage utilizing the third TIA. The reference current may generate a reference voltage at one of the inputs of the gain stage.

A light receiving device that receives a light signal includes: a plurality of avalanche photodiodes, in each of which receiving sensitivity is set in accordance with a bias signal that is provided; a plurality of level conversion units provided in association with the avalanche photodiodes, each of the level conversion units being configured to convert a level of a reference voltage for obtaining the bias signal so as to generate the bias signal and being configured to provide the bias signal to corresponding one of the avalanche photodiodes; and a control unit that generates a first control signal corresponding to a temperature of the light receiving device, and controls a level conversion amount of each of the level conversion units by using the first control signal.

A trans-impedance amplifier arrangement has an input configured to receive an output from a photo-detector, a current monitoring circuit configured in use to provide a current monitor signal dependent on a current through the photo-detector, and an output configured to output said current monitor signal to a control module, said output further configured to receive control information from said control module. A control module is configured to receive the current monitor signal and to provide the control information.