Abstract: The invention relates to a method and arrangements for increasing the dynamic range at an input stage of an optical receiver, which input stage comprises a photodiode acting as a photodetector and an amplifying means the input of which is connected to one terminal of the photodiode. The input of the amplifier is connected to a diode attenuator the dynamic resistance of which is adjusted by means of a direct current proportional to the received optical level and substantially greater than the peak value of the detected signal current. At low levels of the optical signal the diode attenuator is brought into a high-impedance state.

Abstract: A receiver for optical digital signals has a transimpedance amplifier, the input of which is connected to an operating voltage via an active photodiode, and the output of which is connected to an input of a comparator. An operational amplifier is provided, the one input of which is connected to the input of the transimpedance amplifier, and the other input of which is connected to the operating voltage via a further, unilluminated photodiode. A reference voltage at the other input of the comparator is generated from the output voltage of the operational amplifier via a voltage divider.

Abstract: A photoelectric amplifier in a camera exposure system, in which a photodiode is connected across the inputs of an operational amplifier and charges an integrating circuit in a feedback path across the operational amplifier. The resistance of the feedback path can be varied in response to the film sensitivity. The output of the operational amplifier is compared against a films speed reference voltage. Thereby, a reduced range of film speed reference voltages need to be provided because of the optional gain of the photovoltage.

Abstract: There is disclosed an amplifier device for use with a photodetector for amplifying wave energy signals received by the photodetector and converted into electrical signals. The amplifier device includes a first amplifier having its input connected to a junction between the photodetector and first and second photodetector load impedances. A negative feedback amplifier is connected to the output of the first amplifier. The negative feedback amplifier provides a feedback voltage to the first load impedance when in its first mode of operation and effectively reduces the voltage feedback to the first load impedance when in its second mode of operation. A switching device is provided to effectively switch the second load impedance in and out of circuit with the photodetector to effectively change the photodetector load impedance and alter the bias voltage to the feedback amplifier.

Abstract: Herein disclosed are an amplifier and a display which uses the former. The amplifier includes a current amplifying circuit for sending out an amplified output current varying according to an input signal, and a current-voltage converting circuit for converting the output current of the current amplifying circuit into a voltage thereby to generate a high output voltage in response to the input signal. The supply voltage V.sub.cc1 of the current amplifying means and the supply voltage V.sub.cc2 of the current-voltage converting means are set separately of each other to have a relationship of V.sub.cc1 <V.sub.cc2. Thus, a high output voltage can be obtained from the current-voltage converting circuit without the need for the current amplifying means to have high breakdown voltage elements.

Abstract: A high fidelity audio amplifier of the push-pull complementary symmetry type, featuring a feedback circuit with a bias sensing element connected to the output terminals of the output transistors. The feedback circuit includes a photoemitting element in optical communication with a photoconductive element which determines the relative voltage difference of the input terminals of the complementary symmetry output transistors.

Abstract: An attenuator control arrangement for use in a frequency multiplexed communications system includes a light-dependent attenuating resistance which is controlled in normal operation by the level of a pilot tone, in the multiplexed signal being attenuated, being used to control a light-emitting diode which illuminates the light-dependent resistance. A second light-dependent resistance also illuminated by the light-emitting diode is used to provide a control signal for the light-emitting diode in the event that the pilot tone is not detected, whereby a stable attenuation is provided in the absence of the pilot tone.

Abstract: An optical receiver comprises a plurality of sequentially-connected, symmetrically-constructed operational amplifiers having two complementary outputs. For the determination of the operating points and for suppressing the offset voltages, one output of each amplifier is connected by way of a negative feedback path to the second input of the first amplifier, whereas the useful signal is supplied to the first input of the first amplifier.

Abstract: An optoelectronic transducer is proposed which includes a PIN diode (2) that delivers a current that is proportional to a light signal that is received. The diode is connected to the input of an inverting amplifier (4) that delivers a voltage signal v.sub.s. A negative feedback means of the transfer impedance type (6) is connected across the inverting amplifier. The transducer further includes a stabilizing means (8) for the amplifier gain and a temperature drift compensating means (10) for compensating for the drift in amplifier temperature. The stabilizing means (8) includes a detector (26, 28, 32) for the high peak of the signal v.sub.s, and the temperature drift compensating means (10) includes a filter means (38) for producing the means value v.sub.m of the signal v.sub.s, and a comparator (40) that receives the signals v.sub.s and v.sub.m and delivers a signal that reproduces the interference of the light signal that has been received.

Abstract: A function generator which has a plurality of operational amplifiers and a reference voltage generator circuit for applying a different reference voltage to the input terminal of each of the plurality of operational amplifiers. Also included is an LED connected between the output terminal and input terminal of each of the operational amplifiers; photo transistors which receive the emitted light of the LEDs for conversion into a current; and a load resistor which converts the current to a voltage.

Abstract: In an optical receiver for the reception of a modulated light beam, the beam falls on a PIN diode connected to the input of an amplifier which has a feedback resistor across it. This resistor is shunted by the series combination of a Schottky diode and of a PIN diode. The former diode ensures that a high magnitude pulse does not leave the receiver undesirably insensitive to a following smaller pulse. The latter diode, due to its low self-capacitance and low leakage, overcomes distortions due to the Schottky diode's higher self-capacitance and leakage. These effects are enhanced by providing the series-connected diodes with a low value (e.g. 0.2 volts) of reverse bias, due to the different connections of the diodes and the feedback resistor to a potential divider between the amplifier output and a point at a reference potential.

Abstract: A photoelectric current amplifier comprises several partial amplifiers whose outputs lead to a common summing output.

Abstract: An optical receiver of the so-called high impedance type has a photo-diode onto which the modulated light beam from an optical fiber, or received via free space, falls to produce a current in that diode. One end of the diode is coupled directly to the gate of a FET, the other end of the diode being coupled via a capacitor to the source of the FET. The FET's source and its bias resistor are on a source-connected pad. The source output of the FET is coupled via an emitter follower impedance buffer and an equalizing capacitor to a broad-band amplifier. Thus the receiver has a flat overall in-band response.

Abstract: An apparatus for increasing the dynamic range of an integrating input stage in an optoelectric receiver by means of a feed-back (F2) between the output of an amplifier (F1), associated with the stage, and the pole of an optoelectric converter (D) facing away from the input of the amplifier (F1). The gain of the feed-back can be controlled in response to the luminance with the aid of a transducer (G) connected in series with the converter (D).

Abstract: To amplify an input current present at the input of a circuit arrangement with a feedback-coupled operational amplifier, two virtually equal potentials are built up in two different current paths with a common summing point. By means of the potentials, a current flow is produced for each current path. The current flow in one current path is determined by the input current, and the current in the second current path determined by a suitable choice of the impedances on the first and second current paths. The current in the second current path is greater by a multiple than the current in the first current path.

Abstract: A circuit for monitoring the status of electrical signals, such as those present on the control and data lines of an RS-232 interface, includes a single operational amplifier and a dual-color LED indicator. The electrical characteristics of the LED's form a significant part of the circuit parameters. The monitor design provides a predetermined circuit input impedance and positive/negative switching thresholds to effect the selective illumination of the LED's.

Abstract: A light detecting circuit in which noise superposed on a bias voltage of a photodiode is substantially canceled without the aid of a filter circuit employing an inductor. The photodiode is connected between a bias voltage terminal and an inverting terminal of a main amplifier, the latter being implemented with a differential amplifier or a comparator. A capacitance device is connected between the same bias voltage terminal and the other (noninverting) input terminal of the main amplifier. The capacitance device may be either a physical capacitor or a second photodiode which, in either case, should have a capacitance equal to the parasitic capacitance of the first photodiode.

Abstract: A receiver amplifier for amplifying a photoelectric current produced by a light-sensitive semiconductor component. The amplifier includes an amplifier transistor, a capacitor connected between the light-sensitive conductor component and the amplifier transistor for isolating signals with a frequency below a certain threshold delivered by the semiconductor components from the amplifier transistor, and a second transistor connected to the amplifier transistor for producing a current which compensates for changes in the current produced by the light-sensitive semiconductor component in response to light pulses.

Abstract: The front end of an optical receiver circuit (10) is of the type having a field-effect device transimpedance amplifier (16,21) which receives at its input (14) the photocurrent of a photodiode (12). A field-effect device shunt impedance (26) to protect against amplifier overloading is connected between the input and ground through a decoupling capacitor (28). The shunt (26) is controlled by a controller (30), which has its input connected to the output (24) of the amplifier (16) and its output connected to the gate of the shunt (26). The controller (30) compares the output (24) of the amplifier (16) to a threshold reference voltage for determining whether to activate the shunt (26) and regulates the gate voltage of the shunt (26) by means of an AGC amplifier. A direct current feedback resistor (32) is connected between the output (24) of the amplifier (16) and the source of the shunt (26). This prevents the d.c.

Abstract: A broad-band amplifier for the amplification of a photoelectric current triggered by a light signal, including a first transistor connected to receive the photoelectric current, a second transistor connected in series with the first one, a resistance connected between the base of the first transistor and the emitter of the second transistor, a third transistor and a fourth transistor which form a current mirror, the third transistor being connected in series with the second transistor, and a resistance located between the third transistor and ground.

Abstract: A solid state electrical instrument amplifier includes an instrument signal input, a preamplifier, and circuitry in association with the preamplifier and preferably in a feedback loop of the preamplifier, for adjusting the frequency compensation of the preamplifier. The amplifier may also include distortion circuitry, again preferably located in a feedback loop of the preamplifier, which compresses the peaks of the input signal thereby giving a distorted output of the preamplifier which maintains the relative even and odd harmonic content of the input. The amplifier may also include a variable band reject filter operated by a sweep rate generator which varies the light output of a light emitting diode which in turn varies the resistance of photoresistors in the variable band reject filter. If signal delay circuitry is included to create a reverberation effect, the amplifier also includes a high pass filter in parallel with the delay circuitry to increase the high frequency content of the output signal.

Abstract: A three-mode analog controller for regulating a signal corresponding to a controller variable to produce a controller output, comprises an integrating circuit, a proportional circuit, and a derivative circuit. The integrating circuit includes a reset adjustment for varying a time constant thereof, the proportional circuit includes a gain adjustment for varying the gain thereof and the derivative circuit includes a rate adjustment for adjusting the rate of derivation of the signal. The gain adjustment comprises a photoresistor associated with a source of light which is provided with varying current corresponding to the signal to vary the resistance of the photoresistor and, thus, the gain value. The reset and rate adjustments may also comprise photoresistors with light sources or may be formed of field affect transistors each controlled by a circuit and remotely located potentiometer or variable voltage source.

Abstract: An electrosurgical unit having feedforward power regulation. In one embodiment there is an amplifier which produces a pulse modulated electrosurgical output signal. A microprocessor calculates an adjusted pulse width (duty cycle) just sufficient to account for the power changes due to voltage fluctuations. The microprocessor controls the pulse width of the gate voltage of a power transistor in the amplifier to regulate the amplifier output. In another embodiment the supply voltage is fed into the base drive circuitry of an amplifier power transistor through the photo-resistor side of an optoisolator. The lamp brightness of the optoisolator and thus the gain of the base drive circuitry is adjusted by the amplifier power level control. The nonlinearity of the optoisolator complements the nonlinearity of the amplifier so that the net gain in the amplifier drive at any power setting is just sufficient to account for the voltage fluctuation.

Abstract: A nonintegrating, high sensitivity, wide dynamic range receiver is described. A voltage dependent current source is connected in negative feedback with a forward voltage amplifier. The transconductance of the current source is essentially independent of frequency within the signal bandwidth frequency, and the feedback pole is the dominant pole in the loop gain. To prevent saturation by high intensity input signals the receiver is combined with a range extender circuit.

Abstract: A low noise optical receiver utilizes a novel amplifier as the open loop gain element. The amplifier provides for lower noise performance over that of commercial receivers, thus allowing longer fiber optic communication links.

Abstract: A pre-amplifier located "at the focal plane" of a detector array is disclosed which uses MOSFET transistors operated in the "weak inversion" region to provide operational amplifier performance. The dimensions of certain of the transistors are designed to minimize noise amplification. Feedback resistance for the operational amplifier is provided by switched capacitance using MOSFET transistors as switches, thereby permitting adjustment of the amplifier gain. Implanted and non-implanted MOSFET transistors are used in the differential amplifier in such a way as to avoid the need for a biasing network.

Abstract: An audio processor which converts monaural input to a realistic pleasant sounding binaural output in which optical coupling means, having a nonlinear transfer characteristic, creates an unbalanced output to a pair of audio outputs. The system provides for a high or low level input, which may be selected by a switch, to an emitter follower which drives an optical coupling circuit. The optical coupling circuit is comprised of a light emitting diode and a phototransistor connected in a phase splitting network. The phase splitting network provides an unbalanced output to terminals for connecting to preamplifiers, amplifiers, etc. An alternative embodiment employs two optical coupling circuits in two separate signal processing channels, including two phase splitting networks.

Abstract: The use of pulse width modulation rather than analog excitation to control the resistance of a light emitting diode--photoresistor pair is described. In particular, for two LED/LDR opto-isolators in a totem pole configuration, the duty cycle of the first opto-isolator is arranged to equal 1 minus the duty cycle of the second opto-isolator. Thus, both opto-isolators are always active resulting in the ratiometric output being proportional to the duty cycle, and the output impedance being constant.

Abstract: A signal coupling arrangement including a dual detector opto-isolator arrangement operative to transfer a sensed DC signal from an input to an output of an amplifying circuit with an isolated electrical system there between incorporates amplifiers having a specific gain set by unique calibration means and to initially preset the coupling circuitry amplification gains to assure a consistent DC current transfer and DC contrast ratio in coupling DC signals from the input to the output.

Abstract: A new preamplifier for use in fiber-optic receiver applications, or other applications in which a signal detector such as a photodiode is used that exhibits a large input capacitance to the receiver circuitry. The preamplifier combines transimpedance features to generate a voltage output from a current input signal generated by photodiodes used in such applications, and bootstrap features in which the capacitance of the photodiode is bootstrapped to reduce its effect on the receiver.

Abstract: A system input is connected to a positive high voltage signal generator and a negative high voltage signal generator, the outputs of which are each connected to an output terminal via a photoconductor. The photoconductors are driven individually by an energizing circuit which has an input the sum of the system input and an attenuated signal fedback from the output terminal. For system inputs above a first predetermined level or below a second predetermined level, the appropriate photoconductor is rendered heavily conductive so that the output consists of the signal developed by the corresponding signal generator, which is proportional to the system input, less the small voltage drop which occurs across the photoconductor. For system inputs between the two predetermined levels, both high voltage signal generators deliver constant output signals and the energizing circuit reduces the conductivity of the appropriate photoconductor to produce the desired system output.

Abstract: An infra-red receiver front-end includes a trans-impedance amplifier connected to receive an input current and provided with frequency selective transadmittance feedback between its output and input, the transadmittance feedback having a DC path to ground for low frequency noise components in the input current, caused by background illumination.

Abstract: An electronic circuit provides short circuit protection and idle current control for a direct-coupled power amplifier.For short circuit protection, a voltage proportional to output current is monitored and is fed to a light emitting diode (LED). Light energy emitted from the LED as a function of output current is optically coupled to a phototransistor which steals drive current from the input transistor of the output amplifier hence turning off the output transistor.For automatic idling current control, the idle current of a complementary output transistor pair is sampled by operational amplifiers each having an inhibit gate connected from the output of a respective comparator. The comparator produces an inhibit output when the output transistor pair is providing load current to the load. When the pair is not providing load current, the amplifier amplifies the idling current from the pair and provides it to an LED.

Abstract: A light monitoring arrangement, specifically one for monitoring relatively high frequency light pulses and producing corresponding electrical output pulses, is disclosed herein. This arrangement includes circuitry which has the tendency to become electrically saturated if the light pulses being monitored reach or exceed a certain minimum intensity level. This in turn distorts the electrical output pulses in a way which causes these pulses to merge with one another. However, the arrangement disclosed herein also includes circuitry for preventing this from occurring even if the light pulses do reach or exceed circuit saturating intensity levels.

Abstract: Apparatus is provided for sensing the position of a movable member, such as an audio fader control slider (42), and for controlling an operational characteristic of a controlled device (29), such as the gain of an audio amplifier (34), in accordance therewith. A position detector circuit (26) detects the location of the movable member and provides a first signal indicative thereof. A translation circuit (28) responds to the first signal to provide a second signal representing the value assigned to the position indicated by the first signal. The second signal is applied to the controlled device (29) to control its operational characteristic. The position detection circuit (26) includes elements (24, 36, 38) using radiant energy to detect the location of the movable member.

Abstract: An encoder/amplifier giving low distortion, low noise, high power operation. A pair of 180.degree. displaced sawtooth signals are generated from a fixed frequency clock and compared to an undistorted audio input signal. A constant current source and a pair of balanced capacitors are used in this input stage to provide self-nulling of noise. Optical isolation is used between the input encoder and power output stages to eliminate any ground noise occurring on the audio input lines and obviate the need for a large DC power supply transformer.

Abstract: A power supply suitable for energizing an isolation amplifier requiring its input section to be isolated electrically from its output section. The power supply consists of a primary circuit, which, when energized by an electrical supply, converts the electrical energy to infrared radiation, and a secondary circuit which includes a solar cell or cells arranged to receive the infrared radiation. Electrical energy is generated by the solar cell or cells when irradiated. The primary circuit of the power supply includes a plurality of infrared emitting diodes which are energized electrically to provide infrared radiation. The current produced by the solar cell or cells in response to the radiation is applied to a regulating circuit.

Abstract: In one embodiment of the present invention, photocurrents induced in the collector-base junction of a transistor by ionizing radiation incident thereon are compensated by the photocurrent generated by a plurality of series-connected diodes. One feature of the invention includes the selection of the junction areas of the diodes relative to that of the transistor to obtain a predetermined potential at an electrode of the transistor during the incidence of the ionizing radiation.

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: A circuit for limiting the output power of a power amplifier to a preselected value in order to prevent the amplifier from either clipping the input signal or applying potentially damaging signal levels to a loudspeaker connected to the output of the amplifier. The limiting and clipping circuit includes a voltage controlled attenuator through which the input signal passes before entering the amplifier. The amplifier output is compared to an output reference by a control circuit which supplies an attenuation command to the attenuator whenever the output level reaches the reference level. The value of the output reference can be easily adjusted from a fairly low percentage of the amplifier power capacity to the amplifier's maximum power capacity in which condition the circuit prevents amplifier clipping. The circuit is relatively quick to attenuate input signals responsive to excessive output levels, but is relatively slow to reduce the attenuation when the output level is subsequently lowered.

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: Calibration means, including an optiosolator, for a hydrophone preamplifier hich couples to a remote DC supply source and a remote load through a long, two-wire cable. The output signal of the optoisolator is fed to the amplifier in series with the hydrophone output signal, the input to the optoisolator being an AC calibration signal. In an array of preamplifiers, the same calibration signal is fed to all the preamplifiers by connecting the optoisolators in series with each other and the source of the AC calibration signal.

Abstract: An audio signal amplitude detector for applying stereo audio signals above a predetermined amplitude to at least one pair of speakers. The audio signal for each channel is amplified and compared with two reference voltages. When the amplified audio signal is below a lower one of the reference voltages, the signal is blocked to the connected speaker amplifier. As the amplitude of the audio signal increases between the first and second reference voltages, an increasing portion of the audio signal is applied to the connected speaker amplifier until a maximum signal is applied when the amplitude is above the second reference voltage.

Abstract: An isolated signal conditioning circuit is provided whereby control or measurement circuitry is isolated from a load, such as a control instrument, through the use of an optically coupled isolation amplifier. The control or measurement signal is conditioned by the signal conditioning circuit so as to provide a signal to a load, such as a control instrument, which is compatible with the input requirements of the load.

Abstract: Left and right stereo power amplifiers receive power from the 12-volt D.C. automobile supply bypassed by a single capacitor for both amplifiers and energize left and right loudspeakers in series with the junction of the series-connected speakers coupled to ground through a capacitor that allows the left and right speakers to be independently driven by the left and right power amplifiers, respectively, by spectral components above the crossover frequency determined by the speaker impedance and the capacitor impedance. Each power amplifier is driven by an equalizing circuit including a photocell illuminated by an LED that is driven by a feedback signal from the power amplifier.

Abstract: A differential amplifier includes an input stage and an output stage which are electrically isolated from each other to permit the input and output portions of the circuit to be operated at different voltage levels. A pair of optical couplers are employed to couple the differential signal from the input stage to the output stage. The output stage comprises a linear gain cell to provide an output signal proportional to the differential signal through the couplers divided by the common-mode signal through the couplers to stabilize gain and minimize D.C. offset drift caused by small changes in physical parameters or temperature.

Abstract: A signal level stabilizer includes two amplifier stages, each stage having a respective feed-back loop to control its gain. The gains of the amplifiers are varied in response to variations in the level of the input signal to give a substantially constant output signal. At low levels of the input signal the gain of one of the amplifiers only is varied in response to variations of the input signal and at high levels of the input signal the gain of the other amplifier is varied. The amplifiers may be part of a repeater in an optical communications linkage and one of the amplifiers may then be a photodiode and the other a power amplifier.

Abstract: A circuit arrangement for applying low frequency high voltage waveforms across a load and which includes low and high voltage circuits. The low voltage circuit includes a sinusoidal signal generator for producing a low voltage electrical waveform, and a transmitter circuit having first and second light emitting diode circuits by which first and second light signals are generated which are transmitted to the high voltage circuit by respective fibre optic light guides. The high voltage circuit includes first and second high voltage d.c. supplies and first and second triode valves.

Abstract: A complementary transistor output circuit and method incorporates an optical coupler including a light emitting diode and a phototransistor connected between the base electrodes of a complementary pair of output transistors including a PNP transistor and an NPN transistor. The emitter of each of the output transistors is connected to an output of the output circuit. The base electrodes of the PNP output transistor and the NPN output transistor are connected, respectively, to first and second current source circuits. The collector electrode of the NPN output transistor is coupled by means of a first feedback circuit including a first resistor and a PNP transistor to the anode of a light emitting diode. The collector electrode of the PNP output transistor is coupled by means of a second feedback circuit to include a second resistor and an NPN transistor to the cathode of the light emitting diode.

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.