A current Iin is separated into currents I1 and I2. When I1 flows in a light emitting diode D1, the diode D1 emits light and the current path of a phototransistor Q1 becomes conductive. At that time, current Iout flows in a light emitting diode D2. When the diode D2 emits light, the current path of a phototransistor Q2 becomes conductive, and I2 flows. If the value of the current Iout is large, the light emitting strength of the diode D2 is large. A large current I2 flows in the phototransistor Q2, which decreases the value of the current I1 flowing in the diode D1. As a result, the light emitting strength of the diode D1 becomes small, and the value of the current Iout decreases. In this manner, since a photocoupler P2 functions as a negative feedback circuit, linearity of the current Iin and the current Iout improves.

A waveform shaping circuit includes a first parallel circuit including a first capacitance element and a first resistance element coupled in parallel with each other, a positive pulse voltage being applied to a first terminal of the first capacitance element and a second terminal of the first resistance element, a first rectifier circuit disposed between a point of coupling between a third terminal of the first capacitance element and a fourth terminal of the first resistance element and an output terminal.

An input protection circuit (110) for an optocoupler (20) is provided. The input protection circuit (110) includes a first voltage limiter (D1) with a first terminal that is electrically coupled to an input terminal of an amplifier circuit (120), wherein the input terminal of the amplifier circuit (120) is configured to receive a PWM signal and the amplifier circuit (120) is configured to provide a voltage to the optocoupler (20).

Methods and systems for a distributed optoelectronic receiver are disclosed and may include an optoelectronic receiver having a grating coupler, a splitter, a plurality of photodiodes, and a plurality of transimpedance amplifiers (TIAs). The receiver receives a modulated optical signal utilizing the grating coupler, splits the received signal into a plurality of optical signals, generates a plurality of electrical signals from the plurality of optical signals utilizing the plurality of photodiodes, communicates the plurality of electrical signals to the plurality of TIAs, amplifies the plurality of electrical signals utilizing the plurality of TIAs, and generates an output electrical signal from coupled outputs of the plurality of TIAs. Each TIA may be configured to amplify signals in a different frequency range. One of the plurality of electrical signals may be DC coupled to a low frequency TIA of the plurality of TIAs.

An isolation amplifier of an embodiment includes: a primary circuit including an encoder configured to encode an input signal and output the encoded input signal and an anomaly detection circuit configured to detect anomaly having occurred to the input signal and generate a detection signal; an isolation unit configured to insulate the primary circuit from a secondary circuit; an output circuit configured to generate an output signal corresponding to the input signal; and an anomaly-input sensing-output circuit configured to generate an output signal from the secondary circuit by changing the output signal from the output circuit based on the detection signal.

A waveform shaping circuit includes a first parallel circuit including a first capacitance element and a first resistance element coupled in parallel with each other, a positive pulse voltage being applied to a first terminal of the first capacitance element and a second terminal of the first resistance element, a first rectifier circuit disposed between a point of coupling between a third terminal of the first capacitance element and a fourth terminal of the first resistance element and an output terminal.

A signal detection device according to one aspect of the present invention includes a receiver configured to receive a signal including at least a first signal component modulated by a first frequency and a second signal component modulated by a second frequency, and a detector configured to generate, using a base signal, a first reference signal to be used for detecting the first signal component and a second reference signal to be used for detecting the second signal component, perform lock-in detection on the signal received by the receiver using the first reference signal to obtain a first detection signal, perform lock-in detection on the signal received by the receiver using the second reference signal to obtain two second detection signals having different phases from each other, and change at least one of a frequency and a phase of each of the first and second reference signals to set one of the two second detection signals to zero.

A photo-current amplification apparatus is provided. The photo-current amplification apparatus includes a photo-detecting device including: a substrate; an absorption region comprising germanium, the absorption region supported by the substrate and configured to receive an optical signal and to generate a first electrical signal based on the optical signal; an emitter contact region of a conductivity type; and a collector contact region of the conductivity type, wherein at least one of the emitter contact region or the collector contact region is formed outside the absorption region, and wherein a second electrical signal collected by the collector contact region is greater than the first electrical signal generated by the absorption region.

A digital isolator device which includes a first input buffer configured to receive a first differential signal from a transmitter and to provide a second differential signal, the first differential signal being characterized by a first magnitude, the second differential signal being characterized by a second magnitude, the first magnitude being greater than the second magnitude. The device also includes a second input buffer configured to receive a third differential signal from the transmitter and to provide a fourth differential signal, the second input buffer being coupled to the second ground terminal. The device also includes a common-mode circuit coupled to the second differential signal and the fourth differential signal, the common-mode circuit being configured to reduce a common-mode transient voltage, the common-mode transient voltage being associated with a voltage differential between the first ground terminal and the second ground terminal.

Methods and systems for a distributed optoelectronic receiver are disclosed and may include an optoelectronic receiver having a grating coupler, a splitter, a plurality of photodiodes, and a plurality of transimpedance amplifiers (TIAs). The receiver receives a modulated optical signal utilizing the grating coupler, splits the received signal into a plurality of optical signals, generates a plurality of electrical signals from the plurality of optical signals utilizing the plurality of photodiodes, communicates the plurality of electrical signals to the plurality of TIAs, amplifies the plurality of electrical signals utilizing the plurality of TIAs, and generates an output electrical signal from coupled outputs of the plurality of TIAs. Each TIA may be configured to amplify signals in a different frequency range. One of the plurality of electrical signals may be DC coupled to a low frequency TIA of the plurality of TIAs.