Abstract: An integrated circuit includes a principal photo diode connected to the input of a multistage current mirror amplifier. Darlington cascode circuits are integrated into the output branches of the amplifying stages to obviate nonlinear sensitivity of those stages due to Early effect. Each of the cascode circuits have their input base tied to the top end of a diode string through which a current proportional to the photo current is flowing. Thus, there is no DC component in the two supply terminals; in a dark ambient, no supply/signal current flows; and in a light ambient, the supply/signal current is directly proportional to the light intensity.

Abstract: An integrated circuit photo sensor has a principal photo diode whose reverse voltage is maintained at a low and relatively invariant value by a circuit comprised of a biasing diode string in series with a small auxiliary photo diode and an emitter follower coupling the diode string bias voltage to the principal photo diode. This results in reliable starting without contributing a DC component of current in the power supply so this circuit is suitable for use in a linear two-terminal-type integrated-circuit photo sensor.

Abstract: An amplifier, responsive to a photosensitive element operating in a high intensity ambient level, and a method for selecting circuit parameters of the amplifier, take into account differing dynamic mechanisms to provide an optimum tradeoff between signal and noise. The dynamic mechanisms, manifested as electrical noise, affect and are particularly noticeable in the output of the photosensitive element operating in a high energy level environment. The method provides steps for selecting an optimum circuit element for enabling a receiving apparatus to achieve a superior signal to noise figure and hence superior sensitivity to a small AC signal level "riding" on a high DC ambient signal.

Abstract: An optical receiver comprises a photodiode (1) which is connected to a biasing circuit (2), and also to the output (14) of the receiver via the series arrangement formed by a preamplifier (3), a control amplifier 4 and an output amplifier (5), the output of the receiver being connected to the control input 10 of the control amplifier (4) via a detector (6) and a differential amplifier (9). The control amplifier (4) is what is commonly referred to as a differential controller, in which alternating current and direct current are processed in the same manner. As a consequence thereof, it is possible to determine the optical input level of the receiver continuously at the output of the control amplifier by means of a simple ammeter (8).

Abstract: A current mirror amplifier including three or more tandem stages has a photo diode connected, as usual, with one end at the input of the first stage, but with the other end at the input of a third or later stage, which third or later stage is made up of transistors of the same polarity type (NPN) as make up the first stage. Consequently a very low reverse bias is advantageously applied to the photo diode and the linearity and stability of the resulting photo electric device is enhanced with respect to changing input light levels and with respect to variations in DC supply voltage.

Abstract: In a silicon integrated circuit there is formed a silicon photo-diode connected to the input of a multiple stage current-mirror amplifier. The output branch of the amplifier is connected between the two power supply terminals. When voltage is applied to the two power supply terminals the current that flows is the sum of the currents in each branch of the three stage amplifier. Since each branch current is proportional to the current "generated" by the photo-diode, the total power supply current is proportional to the ambient light intensity. Thus a small two terminal photo-conductor type sensor is made that exhibits an unusually high sensitivity that is stable with temperature.

Abstract: A circuit (10) that prevents a photo diode (12) from reaching its saturation output voltage thus ensuring the sensitivity of the photo diode to small changes in radiance at high radiance levels is disclosed. The circuit utilizes a transistor (30) that is allowed to conduct after the output voltage of the photo diode (12) has reached a predetermined level thus shunt loading the photo diode preventing it from reaching its saturation level. A resistor (28)-capacitor (32) time constant circuit is provided preventing the transistor (30) from conducting until the output voltage of the photo diode (12) has reached a predetermined level for a predetermined period of time thus preventing premature conduction of the transistor (30) in response to transient or spurious voltages.

Abstract: A simple method for increasing the dynamic range of a GaAs FET amplifier is described. The drain resistance of the FET is adjusted to induce leakage current across the gate-source junction when excessive power levels are imposed on the gate. This current shunt is provided without added circuit components and therefore does not affect the sensitivity or bandwidth performance of the amplifier.

Abstract: An optical receiver having enhanced dynamic range is achieved through the use of a variable impedance shunt 203 disposed at the receiver input. The optical receiver comprises an optical detector 102 serially connected to a transimpedance amplifier 201. The optical detector 102 receives an optical signal having a variable optical power level and modulation bandwidth and generates a corresponding electrical current therefrom. The transimpedance amplifier provides a fixed amount of gain and converts the electrical current to an output voltage. An automatic gain control circuit 202 produces a control signal which varies in response to the amplitude of the output voltage. The control signal is applied to the variable impedance device to vary the impedance therein. This maintains the output voltage at a predetermined amplitude over the modulation bandwidth without any significant reduction in receiver sensitivity.

Abstract: A correction circuit of a halftone dot area rate detector wherein a relation between a detected halftone dot area rate and a light transmittance or reflectance of an object obtained by a halftone photography is approximately expressed by a turning curve having at least one turning point, which comprises line segments, by using a turning point correction circuit comprising an inverting amplifying circuit, wherein another inverting amplifying circuit is coupled in parallel with the turning point correction circuit, and wherein a potensiometer couples the outputs of the two circuits and outputs a signal corresponding to a correction amount.

Abstract: An improved photodector which in utilizing a low noise load network instead of a resistor has the advantages in signal-to-noise ratio of a large load resistance without the deleterious effect on response time. The circuit includes a conventional photodiode with an operational amplifier at its output. The load network is disposed in the feedback path of the operational amplifier. It consists of a second operational amplifier, a fixed resistor and a variable resistor.

Abstract: A detection circuit is disclosed for use in reflective mode optical mark readers employing LED's as light sources. The subject circuit includes a bias network which sets a contrast threshold for detection and which compensates for temperature variations. The subject detection circuit is ratio dependent rather than magnitude dependent thereby obviating problems which can arise from light sources of different intensities.

Abstract: Monolithically integrable semiconductor circuit with an amplifier controlled by a photo diode, including a differential amplifier having inverting and noninverting inputs and outputs and a photo diode having a first and a second lead, the first lead of the photo diode being connected in the blocking direction to the inverting input of the differential amplifier, and the noninverting input of the differential amplifier being connected to a reference potential, a coupling resistor connected between the inverting and noninverting inputs of the differential amplifier, a filter circuit and a transistor amplifier being connected in a feedback branch between the noninverting output and the inverting input of the differential amplifier, and the inverting output of the differential amplifier and the second lead of the photo diode being connected to ground.

Abstract: A radiant energy system includes an energy receiving member for receiving energy and for converting received energy into electrical signals. Current amplifying means are coupled to the radiant energy receiving member. Voltage comparator means are coupled to the current amplifying means to compare the voltage developed by the current amplifying means to a reference voltage. The comparator provides an output signal indicative of whether the voltage applied to the comparator input is sufficient to actuate the circuit. The output characteristics of the comparator can be selected to be consistent with TTL and data processing circuit drive requirements. The system is suitable for use wherein the radiant energy devices are employed as position indicators for moveable parts and or electrical isolation of postage meters.

Abstract: The present invention comprises a low gain amplification circuit for amplifying the output of a light detecting transistor and producing a logic outputstrong enough to drive standard transistor logic circuitry. One or more bipolar non-symmetrical transistors are arranged in a cascade connected circuit to produce an amplification gain less than that of a single conventional transistor. The bipolar non-symmetrical transistors are reverse connected between the high level and low levels of the power supply and all feedback lines are eliminated while the frequency response is substantially increased.

Abstract: An optical comparator having a transimpedance amplifier with feedback diodes coupled to a differential pair of transistors which have transfer functions matching those of the feedback diodes provides a linear interpolated signal in response to the comparison of two light signals.

Abstract: A pre-amplifier for photomultiplier tubes includes means to compensate for the combined dark current and noise output of a photomultiplier tube without inducing a noise dependent offset voltage at the pre-amplifier output. A feedback amplifier and a compensating network, including a capacitor, cooperate to monitor the pre-amplifier output and during this time to maintain the feedback amplifier in a linearly responsive state while charging the capacitor to an amount necessary to clamp the average value of the most negative excursion of the pre-amplifier output to ground.

Abstract: Disclosed is an amplifier for electrical signals obtained by means of a photoelectric transducer as a function of the intensity of illumination incident upon said transducer, comprising an operational amplifier adapted to be connected in series after the photoelectric transducer and having a feedback branch, wherein the feedback branch of the operational amplifier includes an electrical element having a nonlinear characteristic connected in parallel with a resistance.

Abstract: A photometric amplifier circuit, having a photocurrent converting element connected between a pair of inverting and noninverting input terminals of a differential amplifier, for amplifying an electric signal responsive to the quantity of light, is characterized in that a differentiating circuit is connected between the inverting input terminal of the differential amplifier and a power supply to thereby prevent the differential amplifier from producing an undesired latch output when the power is supplied from the power supply, with the result that, after this power is supplied, a normal amplifying operation is capable of being obtained at an earlier time. This invention is particularly adapted for an automatic exposure control system for cameras to precisely control the exposure of the camera.

Abstract: A light-emitting diode of a photo-coupler is energized and de-energized through a connection to a switching means. Radiation from the light-emitting diode directed toward a photosensitive means of the photocoupler, reduces the resistance of the photosensitive means to rendering a switching transistor conductive. The switching transistor is connected to and controlled by the photosensitive means. When the switching means is open, the switching transistor remains conductive for a predetermined time period due to a transient phenomena of a resistance change of the photosensitive resistor.

Abstract: A novel photodetector circuit utilizing both the generated photovoltage, as well as its inverse, to improve the signal-to-noise ratio at the optical receiver output.

Abstract: A circuit useful in replicating the current produced in a photo diode operated as a current source at zero bias. A second scaled area photo diode is used to bias the circuit to maintain the zero bias over a wide range of illumination levels. The circuit operates in the picoampere range and is linear over at least six orders of magnitude.

Abstract: A two-terminal photodetector comprising a photodiode and a plurality of active and passive components connected so that when connected to a source of current the voltage across the terminals is proportional to the illumination and is proportional by an amplification factor to rapidly changing illumination levels.

Abstract: A novel form of photoelectric conversion circuit including a photo sensor is provided, which is very limited in response time even at low illuminations and highly valuable for use in automatic cameras. It comprises a comparator for comparing the output voltage of the operational amplifier, connected to the photo sensor, with a reference voltage, and discharging means operable under the control of the comparator quickly to discharge the charge stored in a parastic capacitor of the photo sensor when the circuit is energized for operation.

Abstract: An opto-electronic coupler for signal voltages of <1 V is provided in which the transmitter of the coupler is electrically separated from the receiver. In order to avoid a current supply device, there are provided two additional couplers connected in series and of opposite coupling direction to the first coupler. The additional couplers supply the necessary energy for a luminescent diode transmitter of the first coupler.

Abstract: A photoelectric current log-compression circuit includes a log-conversion diode, a photodiode and an operational amplifier for log-compression. In the negative feedback circuit of the operational amplifier is inserted a thermistor to control the amplification degree of the operational amplifier according to the current flowing through the log-conversion diode. Further, a forward voltage of a temperature compensating diode biased with a constant current is applied to the reference voltage of the operational amplifier.

Abstract: A differential amplifier has one input connected to a reference potential and a photo diode connected in series with a level shift to the other input. A negative feedback loop is also coupled into other input. This stabilizes the amplifier and, if the level shift is made equal to the reference potential, biases the photo diode to zero, thereby reducing leakage current. A second feedback loop is used to adaptively bias the tail current in the differential amplifier.

Abstract: A simple, reliable and sensitive electrical circuit for detecting when a first input exceeds a second input and vice versa and producing corresponding signals at first and second outputs comprising first and second operational amplifiers each having its negative input connected to its output and its positive input serving as a circuit input to function as a voltage follower, first and second comparator circuits with the positive input to the first comparator being directly connected to the output of the first amplifier and the negative input to the output of the second amplifier via voltage dividing resistors so that the output thereof goes to zero when the output of the first amplifier drops below the divided output of the second and with the second comparator similarly connected so that the output thereof goes to zero when the output of the second amplifier drops below the divided output of the first amplifier.

Abstract: A system for detecting the edges of a moving object is disclosed having a high flux density light beam directed through two relatively long narrow light beam apertures and focused on a detector to saturate the output of the detector. When the moving object interrupts the light beam, the detector remains saturated until the moving object nearly intersects the entire light beam to thereby deactivate the detector at a precisely defined predetermined location within the light beam. The moving object reactivates the detector when its trailing edge intersects the light beam at a second precisely defined location within the light beam. An amplifier operating in saturation mode is coupled to the output of the detector to provide the added feature of switching its output when the object is at very precisely defined locations within the light beam.

Abstract: A signal transformation network which is uniquely characterized to exhibit a very low input impedance while maintaining a linear transfer characteristic when driven from a voltage source and when quiescently biased in the low microampere current range. In its simplest form, it consists of a tightly coupled two-transistor network in which a common emitter input stage is interconnected directly with an emitter follower stage to provide virtually 100 percent negative feedback to the base input of the common emitter stage. Bias to the network is supplied via the common tie point of the common emitter stage collector terminal and the emitter follower base stage terminal by a regulated constant current source, and the output of the circuit is taken from the collector of the emitter follower stage.