Abstract: The present invention provides an illumination management system that includes a first LED that outputs a first signal when exposed to a first spectrum of light, the first signal indicating an intensity of light from the first spectrum; a second LED that outputs a second signal when exposed to a second spectrum of light, the second signal indicating an intensity of light from the second spectrum and wherein the second spectrum includes at least some wavelengths that are not in said first spectrum. In some embodiments, more LEDs could be included in the system for associating the presence of light energy from different parts of the light spectrum. Also included is light control circuitry, coupled to the LEDs, configured to generate a lighting control signal that can be output to one or more lights to adjust the lights to a desired light level, wherein the lighting control signal varies in response to said first and second signals.

Abstract: A supply assembly for a LED lighting module, comprising a supply unit to which the LED lighting module can be connected and a burst control unit which is capable of switching the power supply unit on and off with a burst frequency (fburst) so as to control the mean light output. Preferably, the burst control unit is provided with a pulse duration modulator for controlling the pulse length (T pulse) during which the supply unit is operative.

Abstract: A charging/discharging circuit comprises a PNP transistor controlled by a diode, an NPN transistor arranged on a discharging path and controlled by at least one photodiode, and a capacitor arranged between a photodiode and the NPN transistor. During charging stage, a charging current flows through the diode to produce a voltage drop, which cuts off the transistors to prevent leakage current. The photodiode generates a photo current such that the capacitor presents a negative voltage on one contact thereof, which facilitates the discharging process.

Abstract: A transistor photoelectric conversion drive circuit to excite coupled photoelectric conversion device by electric energy driven light emission device or natural light source in the environment to generate electric energy of positive voltage to drive metal-oxide-silicon field effect transistor (MOSFET) or insulated gate bi-carrier transistor (IGBT) or any other high input resistance transistor while electric energy is stored at a slave negative voltage supply circuit device by means of the electric energy of positive voltage so that upon the signal of positive voltage is cut off, negative voltage is inputted to gate and emitter of one or more than one high input resistance transistors to facilitate cutoff.

Abstract: A monolithically integrated heterojunction bipolar transistor optoelectronic transimpedance amplifier using the first transistor as an optical detector. An edge illuminated epilayer waveguide phototransistor is used as the light-detecting element. The phototransistor is used as an optical detector in which the incident light pulses are converted to electrical pulses and then amplified for further signal processing. The phototransistor is monolithically integrated on the same material substrate as the emitter follower amplifier so that the parasitics normally associated with receiver circuitry are minimized. By eliminating the parasitic impedances, the circuit can be used as a receiver in high bit rate optical communication systems.

Abstract: An LED lamp package for packaging an LED driver with an LED is provided. In one embodiment, the LED lamp package includes an LED driver chip and an LED chip, both of which are mounted on the ground lead of the LED lamp package and both of which are enclosed by the light transparent encapsulant of the LED lamp package. In another embodiment, the LED chip is mounted on top of the LED driver chip in the LED lamp package. In this embodiment, the LED driver chip includes an attachment pad, on which the bottom surface of the LED chip is mounted.

Abstract: A method for calibrating photoelectric cells is described, which is based on a single acquisition step, of an object or of the background of the detection field of the photoelectric cell, respectively. The method allows carrying out a faster calibration with respect to the traditional dual-acquisition calibration method. In an embodiment, the two acquisition methods can be alternatively used at the discretion of the user.

Abstract: A programmable logic controller with enhanced and extended the capabilities. A digital input filter implement filters with considerable less logic by simulating the action of a capacitor being driven by a constant current source whose output voltage is sensed by a comparator with a large amount of hysterisis. A pulse catch circuit captures the input pulse even though the update occurs between scan cycles. A pulse output controller includes a hardware pipeline mechanism to allow for smooth, hardware-controlled transitions from wave-form to wave-form. A free port link allows the user to control the port either manually or by operation of a user program. In order to provide higher performance for communication using PPI protocol, the PLC includes a built-in protocol. An n-bit modem protocol ensures data integrity without use of a parity type data integrity system.

Abstract: An optocoupler having a driving traic and at least one normally-on driving element couple in series to the driving triac. A light emitting element turns on the driving triac at a time when a phase of a load current is at about 0°. The normally-on driving element is composed of either a MOSFET, or optionally a relay, and an associated element for turning off MOSFET, or relay, at a time when a phase of the load current is about 90°. The arrangement prevents an inrush current or commutation failure, and provides an optocoupler which can be turned off with prescribed timing. Alternative embodiments are disclosed for an optocoupler that can turn itself off when an abnormality occurs, for example, when an ambient temperature rises to an extremely high level.

Abstract: A Light Emitting Diode (LED) driver circuit with a boosted voltage output for driving an LED from a voltage power supply having a voltage that is lower than the turn “on” voltage of the LED is provided. A charge pump provides the boosted voltage output of the LED driver circuit. During operation, the LED driver circuit switches the LED on and off at a predetermined frequency such that a human observer perceives the LED to be continuously turned “on”. In one embodiment, the LED driver circuit further comprises a current regulator for regulating the current supplied to the LED. In another embodiment, the LED driver circuit comprises a voltage regulator to regulate the boosted voltage output of the LED driver circuit.

Abstract: A Light Emitting Diode (LED) driver circuit with a boosted voltage output for driving an LED from a voltage power supply having a voltage that is lower than the turn “on” voltage of the LED is provided. A charge pump provides the boosted voltage output of the LED driver circuit. During operation, the LED driver circuit switches the LED on and off at a predetermined frequency such that a human observer perceives the LED to be continuously turned “on”. In one embodiment, the LED driver circuit further comprises a current regulator for regulating the current supplied to the LED. In another embodiment, the LED driver circuit comprises a voltage regulator to regulate the boosted voltage output of the LED driver circuit.

Abstract: An optical communication device includes a receiving circuit that generates an accurate voltage signal from received light. The voltage signal is then used to quickly and accurately determine emission information which is used to adjust the emission level of an associated light emitting diode, by varying the drive current supplied to the light emitting diode. The receiving circuit has a light receiving element that generates a current from received light. The current is converted into first and second current signals using a fixed distribution ratio. First and second amplifiers convert the first and second current signals to first and second voltages. A current control circuit is connected to the light receiving element and the second amplifier and controls the amount of the first current signal using the second voltage.

Abstract: A pixel sensor system that includes a photo-sensor, an output amplifier, and a feedback capacitor. The photo-sensor is configured to receive photons and to convert the photons into charge. The output amplifier has at least two transistors in a cascoded configuration. The amplifier converts the charge into electronic signal. The feedback capacitor is disposed between the photo-sensor and an input of the output amplifier.

Abstract: An amplification type solid state imaging device output circuit includes a source follower circuit and a current mirror circuit. The source follower circuit is formed of a first MOS transistor Q11 and a second MOS transistor Q15 that is used as a load and is connected to the first MOS transistor Q11 via a vertical signal line. The current mirror circuit is formed of the second MOS transistor Q15 and a third MOS transistor Q21 which has the same channel structure and in which the gate and the drain are connected to the gate of the second MOS transistor Q15. The drain of the third MOS transistor Q21 is connected to a power source via a fixed resistor R11. The variation in the current flowing through the fixed resistor R11 and the third MOS transistor Q21 is reduced, and therefore, the variation in the current of the second MOS transistor Q15 used as a load can be reduced, allowing a wide operating margin to be secured.

Abstract: An opto-isolator circuit for providing isolation between a bi-directional, I2C transmission line and a pair of single-direction transmission lines. The opto-isolator circuit includes a bi-directional port for receiving data from, and providing data to, the bi-directional transmission line. The circuit further includes an output path that has (i) a first buffer for receiving outgoing data from the bi-directional port, (ii) a first opto-isolator for receiving the outgoing data from an output of the first buffer, and (iii) a second buffer for receiving the outgoing data from an output of the first opto-isolator and providing the outgoing data to an output port. The circuit also includes an input path, that has (i) a third buffer for receiving incoming data from an input port, (ii) a second opto-isolator for receiving the incoming data from an output of the third buffer, and (iii) a fourth buffer for receiving the incoming data from an output of the second opto-isolator.

Abstract: The invention concerns an output circuit for extracting the avalanche pulse produced by an avalanche photodiode for single photon detection (Single Photon Avalanche Diode, SPAD), which makes possible to detect and measure with the best possible precision the time of arrival of an incident photon on the surface of said SPAD. The circuit is built with a coupling network, connected to a terminal of said SPAD biased at high voltage and a comparator. Said network is designed so that the differentiation time constant, introduced by said block, is less than the total duration of the avalanche current pulse, but longer than the risetime of said pulse (FIG. 5 and FIG. 8). The circuit object of the invention has the virtue of being usable in all the circuit configurations for avalanche quenching in SPADs described in the technical and scientific literature.

Abstract: An electronic circuit arrangement has a receiving component that detects an incoming physical signal, and supplies an electrical signal current in response thereto, as well as a control and analysis component which is fed by a supply voltage and is acted upon by the electrical signal current. The electronic circuit arrangement can be operated in a working state, in which a power is consumed, and in a rest state, in which no power is consumed. A quiescent current detector is connected in parallel to the receiving component and the control and analysis component. In the rest state of the circuit arrangement (when the supply voltage is switched off), the quiescent current detector detects the signal current supplied by the receiving component, and controls switching-on of the circuit arrangement into the operative state in response thereto.

Abstract: An interpolation circuit for an optical encoder or other sensing device includes a signal generating circuit, a comparator circuit and a logic circuit. The signal generating circuit generates A, A′, B, B′, one or more fractional A or A′ and one or more fractional B or B′ ramp signals in response to input ramp signals that are one quarter cycle out of phase. The comparator circuit compares selected pairs of the A, A′, B, B′, one or more fractional A or A′ and one or more fractional B or B′ ramp signals and generates intermediate signals. The phases of the intermediate signals are preferably uniformly or nearly uniformly distributed in phase with respect to the ramp signals. The logic circuit combines the intermediate signals and provides first and second output signals, each having multiple cycles of the ramp signals. In one embodiment, the signal generating circuit generates A, A′, B, B′, A/3 or A′/3 and B/3 or B′/3 ramp signals.

Abstract: A photodetector circuit that operates a reduced power levels is provided. The photodetector circuit preferably includes a control circuit that alternates between an active mode and a standby mode. During an active mode, information regarding the relative strength of a light signal is acquired and reported. However, during a standby mode, portions of the photodetector are disabled or turned off so that no information regarding a light signal is acquired or reported and overall power consumption is reduced.

Abstract: An on-chip system and method for calibrating an illumination source includes a photo-detector and intensity sense and control circuitry resident on an integrated circuit. The integrated circuit is illuminated by an illumination source, which impinges upon the photo-detector. The intensity sense and control circuitry receives the measured intensity value of the illumination source and compares the measured intensity to a predetermined value representing the desired intensity. Subject to a range of operation, the intensity sense and control circuitry adjusts the intensity of the illumination source based upon the difference between the measured illumination intensity and the desired illumination intensity.

Abstract: There is provided an electro-optically driven relay system (10) for switching the application of energy to a load (5). The subject relay system (10) comprises: a switch unit (100) operable responsive to a control signal; an electro-optic current generating unit (200) connected to the switch unit (100) for generating the necessary control signal responsive to an actuation signal; and, primary and supplemental drive units (300, 400) connected to the electro-optic current generating unit (200) for collectively generating the actuation signal. The primary drive unit (300) is operable responsive to a first input signal; and, the supplemental drive unit (400) is operable responsive to a second input signal to augment the actuation signal for at least a predetermined time duration. The switching response of the switch unit (100) is thereby accelerated.

Abstract: A semiconductor dark image position sensing device comprises a photoelectric layer generating a photoelectric current in a portion where light is input in response to intensity of the light input, a resistive element layer into which the photoelectric current generated in the photoelectric layer flows from a portion corresponding to the position of light input, a second resistive element disposed in association with the photoelectric layer for replenishing an insufficient amount of electric current with respect to the photoelectric current so as to flow the same into the resistive element layer in such that a distribution of electric current flowing into the resistive element layer corresponding to the position of light input becomes substantially uniform over a whole sensing region, and signal electric current output terminals disposed at the opposite ends of the second resistive element.

Abstract: A display and keyboard illumination of battery-operated portable electronic devices using LEDs are provided. A flyback converter is modified into a dedicated converter suitable for using two LEDs and their diode-like operation is utilized. Firstly, a specified amount of energy of the battery voltage (Vbatt) is stored in the coil (L) of a primary circuit until, controlled by a comparator (K). The LEDs are connected in parallel with the coil, in direction such that they substantially prevent the current leaking through them. Secondly, the coil is disconnected from the battery by a switch (SW). A comparator (K) detects when the coil current reaches a specified threshold level and, by using a control circuit (SWC), then causes the switch (SW) to become non-conductive. The self-induction of the coil builds up a voltage exceeding the forward bias of the LEDs, which (thirdly) keeps on passing the current and illuminating.

Abstract: The present invention comprises an operational algorithm, and calibration process, for an avalanche photodiode (ADP) receiver which takes into account an APD behavioral model. In-situ optical and electrical measurements (calibration) of the APD are performed to determine key constants for use in the model. Knowledge of these constants allows for optimum operation of the APD over a wide range of input optical power. The operational algorithm also gives an estimate of input optical power over a wide range of ambient temperatures.

Abstract: A measuring device for measuring the intermediate circuit voltage of a gradient amplifier of a magnetic resonance imaging apparatus has a measuring circuit with a potential-dividing connection to a voltage indicator, the measuring circuit being connected in series with a discharging resistor of the intermediate circuit capacitance, and being driven from the discharging current via the discharging resistor.

Abstract: The invention concerns an output circuit for extracting the avalanche pulse produced by an avalanche photodiode for single photon detection (Single Photon Avalanche Diode, SPAD), which makes possible to detect and measure with the best possible precision the time of arrival of an incident photon on the surface of said SPAD. The circuit is built with a coupling network, connected to a terminal of said SPAD biased at high voltage and a comparator. Said network is designed so that the differentiation time constant, introduced by said block, is less than the total duration of the avalanche current pulse, but longer than the risetime of said pulse (FIG. 5 and FIG. 8). The circuit object of the invention has the virtue of being usable in all the circuit configurations for avalanche quenching in SPADs described in the technical and scientific literature.

Abstract: An optical coupling semiconductor switching circuit to be coupled to a light emitting device for controlling electric circuits. The switching circuit includes a light detector generating voltage in response to light from the light emitting device and an impedance circuit having a first and a second output terminal. The impedance circuit is connected to the light detector and passes through a voltage input from the light detector to the output terminals with little loss. A plurality of switching devices are connected in parallel between the output. Each switching device includes at least a pair of transistors each having a gate connected to the first output terminal, and an optical rectifier that is activated by light from the light emitting device. The rectifier has a cathode connected to a source of each transistor and a anode connected to the second input terminal.

Abstract: The invention relates to an optical receiver comprising a transimpedance amplifier (21) and a photo detector (PD) for converting the optical power arriving at the receiver into electric current. To enable a good dynamic range to be achieved for the receiver in a simple way, the transimpedance amplifier is a differential amplifier provided with two inputs. Furthermore, the receiver comprises separating means (LPU) for separating a direct voltage component from the output voltage of the transimpedance amplifier and means (VCU) for supplying a direct voltage dependent on the direct current component to that input of the transimpedance amplifier which is different from the input used by the photo detector.

Abstract: A light detection device has a biasing transistor (1) arranged to provide a bias current and a reverse biased transistor. The reverse biased transistor has a drain terminal (6) coupled via a high impedance resistor (4) to the supply voltage. Incident visible light is detected by a voltage drop at the drain electrode.

Abstract: A pulsing circuit for producing an output signal having a high amplitude pulse and a low amplitude pulse may comprise a current source for providing a high current signal and a low current signal. A gate circuit connected to the current source includes a trigger signal input that is responsive to a first trigger signal and a second trigger signal. The first trigger signal causes the gate circuit to connect the high current signal to a pulse output terminal whereas the second trigger signal causes the gate circuit to connect the low current signal to the pulse output terminal.

Abstract: A CMOS charge-integration mode photo-detector built on an n-type substrate is disclosed in this invention. This photo-detector includes a p+n photodiode with the n-type substrate constituting an n-region and a p+ diffusion region disposed near a top surface of the n-type substrate, the p+ diffusion region constituting a charge integration node. The photodetector further includes a gate-biased charge storable n-type MOS transistor functioning as a photo-conversion voltage amplifier supported on the substrate formed with a threshold voltage of Vt0 having a gate terminal connected to the charge-integration node. The photodetector further includes a MOS transistor supported on the substrate functioning as a constant current-source load transistor having a drain terminal connected to a source terminal of the gate-biased charge storable n-type MOS transistor and a gate terminal connected to a bias reference voltage.

Abstract: Gain and error correction circuitry for metal-oxide-semiconductor (MOS) analog storage circuits, including image sensors. The correction circuitry allows the analog output signal for a storage cell to substantially track an input signal in each cell. Voltage dependent distortion and attenuation in the output signal, with respect to the input signal, is minimized, without significantly increasing the size of each cell.

Abstract: A circuit arrangement for making isolated voltage and/or current measurements on a transmission line is characterized in that a shunt branch between the go conductor (+) and the return conductor (−) contains a series combination of a transformer (T), a first optically controllable, clocked switching element (OS1), and a first resistor (R1), and/or that the go conductor (+) or the return conductor (−) contains a second resistor (R2) shunted by a series combination of a transformer (T) and a second optically controllable, clocked switching element (OS2). The measured voltage and current values can thus be taken off linearly to the voltages and currents of the transmission lines using simple means and only few active components, particularly without analog-to-digital converters and power supplies tied to the potential of the transmission line.

Abstract: A PLZT optical shutter array includes an optical shutter array, a driving circuit, a temperature compensating circuit, an IC control unit, a driving IC and a temperature sensor. Temperature of the optical shutter array is detected by the temperature sensor, and based on a voltage representing the temperature and a reference voltage for driving optical shutter element, a driving voltage for the optical shutter element is generated in the temperature compensating circuit. The driving voltage is applied to the optical shutter element through the IC control unit and a driving IC. As a result, a voltage applying apparatus for a light signal emitter which has a simple structure and allows cost reduction is provided.

Abstract: Circuitry capable of controlling a bias voltage for an avalanche photodiode (APD) in accordance with the temperature slope of the breakdown voltage of the APD is disclosed. A reference voltage generating circuit sets a voltage implementing an optimal amplification ratio on an output terminal, and generates a reference voltage by taking account of the temperature slope of the breakdown voltage of the APD. The reference voltage is applied to one input of a voltage comparator. A setting circuit feeds to an adding circuit a preselected voltage for controlling the voltage on the output terminal to a value capable of implementing the optimal multiplication ratio. A temperature compensating circuit feeds to the adding circuit a voltage corresponding to the temperature slope of the above breakdown voltage. The temperature slope is representative of the variation of the breakdown voltage with respect to temperature.

Abstract: A method for providing an improved active pixel sensor cell having a soft-saturation circuit. The method includes providing a pixel node and a photodiode coupled to the pixel node. The photodiode receives light and converts the light into an electrical signal representative of light. A soft-saturation circuit for selectively affecting the electrical signal at the pixel node based on the electrical signal at the pixel node based on the electrical signal at the pixel node is also provided.

Abstract: A differential charge and dump optoelectronic receiver for baseband digital optoelectronic data links is disclosed having a preamplifier and a voltage controlled current source that defines the tail current of a differential pair functioning as a two quadrant multiplier, and using capacitors as loads on the differential pair making said differential pair an integrator. The integrator provides a full differential output, part of which is fedback to control the gain of the preamplifier. In a preferred embodiment, one integrator pair is used to recover the data from a Manchester encoded data stream. In another preferred embodiment, two pairs of integrators are used for QPSK like codes.

Abstract: An image sensing cell includes: a light sensing device 18; a first transistor 10 having a first node coupled to the light sensing device 18; a second transistor 12 having a first node coupled to a second node of the first transistor 10; a third transistor 14 having a control node coupled to the light sensing device 18; and a fourth transistor 16 having a first node coupled to a first node of the third transistor.

Abstract: An apparatus and method for improving dynamic rays and motion representation in digital imaging. A light sensitive element such as a photo diode is employed to sense a light level at a surface during a period of time. A plurality of storage elements are associated with the light sensitive element but electrically segregated therefrom by a plurality of sampling transistors by enabling the sampling transistors between the particular storage element and the light sensitive element in a predetermined way. Its dynamic range can be extended and since readout between exposures is not required, exposure may be taken in closer temporal proximity thereby improving motion representation.

Abstract: An IC is configured by using a circuit form comprising a CMOS and also a new current inverter element, thereby to reduce current consumption of ICs having a function of converting an output from a photodiode or the like to a voltage and a function of amplifying the output.

Abstract: Between a reference voltage point and the emitter or the source of a transistor of which the collector or the drain is connected to a power source and to which an signal is input at its base or its gate, DC current passing means for causing a current to flow from the emitter or the source to the reference voltage point and a capacitor connected to the reference voltage point at one end and charged with a voltage generated in the DC current passing means are provided. A detection output for the signal is obtained from the emitter or the source of the transistor, or the other end of the capacitor.

Abstract: A CMOS charge-integration mode photo-detector built on an n-type substrate is disclosed in this invention. This photo-detector includes a p+n photodiode with the n-type substrate constituting an n-region and a p+ diffusion region disposed near a top surface of the n-type substrate, the p+ diffusion region constituting a charge integration node. The photodetector further includes a gate-biased charge storable n-type MOS transistor functioning as a photo-conversion voltage amplifier supported on the substrate formed with a threshold voltage of Vt0 having a gate terminal connected to the charge-integration node. The photodetector further includes a MOS transistor supported on the substrate functioning as a constant current-source load transistor having a drain terminal connected to a source terminal of the gate-biased charge storable n-type MOS transistor and a gate terminal connected to a bias reference voltage.

Abstract: An active input circuit module includes a plurality of active input circuits disposed on a circuit board each circuit having an input and a return. Each active input circuit further has a constant current source having a current source input and a constant current output coupled through a current limiting resistor to an opto-coupler input and the return. A shunt resistor is coupled in parallel with the opto-coupler input.

Abstract: A bias voltage supply circuit for an optical receiver includes a high-voltage generation circuit, a current detection circuit, a reference voltage generation circuit, and an operational amplifier. The high-voltage generation circuit supplies a variable bias voltage to an APD having an amplification function. The current detection circuit converts an output current, which is based on the bias voltage supplied from the high-voltage generation circuit, into a voltage signal. The reference voltage generation circuit outputs a constant reference voltage. The operational amplifier outputs a voltage control signal, corresponding to a difference between an output voltage from the current detection circuit and the reference voltage from the reference voltage generation circuit, to the high-voltage generation circuit, thereby variably controlling the bias voltage to be supplied to the photoelectric converting element.

Abstract: A method and apparatus for measuring very low light signals including integrating a signal from a photo diode, avalanche photo diode, photomultiplier tube or the like, digitally sampling the integrator output more than two times during each integration period, fitting a curve to the multiple digitized readings to calculate the integration slope for each integration period and determining the original signal from the calculated integration slope.

Abstract: A light sensing apparatus for different control systems includes a photosensitive element which generates a light current depending on light incident thereto. A pre-circuit connected to the photosensitive element is operative for generating separate basic signals in response to the light current generated by the photosensitive element. Processing circuits connected to the pre-circuit are active simultaneously for converting the basic signals generated by the pre-circuit into conversion-resultant signals having different forms respectively. The conversion-resultant signals are outputted to the control systems respectively. At least one of the processing circuits may include an oscillation circuit which oscillates at a frequency depending on related one of the basic signals generated by the pre-circuit.

Abstract: An improved opto-isolator circuit is disclosed. A fixed bias current is induced through a photoemitter of the opto-isolator. A fixed DC voltage is fixed across the sensor of the opto-isolator, whereby any unknown scaling factor in the opto-isolator is substantially eliminated. In a low frequency embodiment, a passive bridge is used while in a high frequency embodiment, an active bridge circuit is used.

Abstract: A converter for providing an electrical signal according to the status of a light spot applied thereto, comprises: a sensor for sensing the light spot and generating a position current according to the position of the light spot sensed thereat; and an operating circuit for providing the sensor with an operating current when the light spot is sensed by the sensor and for outputting a status current corresponding to the operating current. The sensor comprises two electrodes each providing a current with magnitude determined according to the distance between it and the position of the light spot sensed thereat. The position current is obtained by subtracting the first electrode current from the second electrode current.

Abstract: When a third transistor receives first photoelectric currents outputted from a sensing photodiode, the third transistor provides second photoelectric currents to bases of a first transistor and a second transistor, then the first transistor turns on and carries the first photoelectric currents, so first currents corresponding to the first photoelectric currents flow to a first terminal. Thus, the first photoelectric currents can be directly outputted from the first terminal. On the other hand, the second transistor also turns on and carries second currents corresponding to amplified first photoelectric currents, so the second currents flow to a third terminal. Thus, the amplified first photoelectric currents can be outputted from the third terminal.

Abstract: A circuit for protecting a laser indicator is disclosed in which a current amplifying circuit composed of two transistors drives a laser light emitting diode (LED) to generate a laser light. A base of one of the two transistors connects with a protective resistor and a variable resistor. The variable resistor is used to control the magnitude of a base current of the transistor and the protective resistor is used to prevent an overrating current. A diode is further coupled to a positive power input terminal of the current amplifying circuit to prevent the circuit for protecting a laser indicator from being damaged due to being reversely connected the polarities of the power source. Through a design of such a circuit, a stable laser light-spot is achieved and the components in the circuit will not be damaged.