Abstract: A split-path isolation amplifier (10) employs a transformer (30) in a high path (26) and a single-input, dual-output closed-loop optocoupler (66) in a low path (24) to achieve a flat, wide frequency response without need for frequency compensation adjustments. In a low path frequency region (106), the optocoupler provides all or most of the signal to the output. The isolation amplifier employs a substantially overlapped crossover frequency region (104) in which the high path signal is applied to a primary winding (28) of the transformer, and the low path signal is applied differentially to secondary windings (40, 42) of the transformer. At frequencies below the crossover frequency range, the signal from the optocoupler dominates as the signal coupled from the primary winding rolls off. At frequencies above the crossover frequency range, the signal coupled from the primary winding dominates as the signal from the optocoupler rolls off.

Abstract: An amplifier circuit having a pre-amplifier responsive to a program input signal, a filter circuit, and an absolute value circuit. The pre-amplifier provides automated balancing between the high frequency channel signals and the mid range channel signals to provide a compensated signal. The filter circuit is coupled to receive and automatically filter the compensated signal to provide an output signal and a modified compensated signal. The filter circuit has an adjustable bandwidth that is automatically adjusted in response to the control signal for automatically reducing the bandwidth of the filter circuit in response to lower values of the control signal to obtain the output signal. The filter circuit uses a voltage controlled amplifier or a photo cell in combination with an integrator. An absolute value circuit senses the modified compensated signal and provides a control signal proportional to the average peak value of the amplitude of the modified compensated signal.

Abstract: An amplifier circuit provides wide bandwidth low noise performance by minimizing the effect of a pole created by the feedback resistor and the capacitance of the input device, such as a photodiode. This is accomplished by shifting the dominant pole to higher frequencies in the amplifier disclosed. A first amplifier stage receives a signal from an input device, such as the photodiode, and feedback from a second amplifier stage. The first amplifier stage is connected to the second amplifier stage such that a lower gain stage is employed to eliminate the phase shift which occurs if the amplifier alone is used in open loop form. The output of the low gain stage is provided to a second amplifier stage with associated gain setting components such that the dominant pole of the overall amplifier is shifted to a higher frequency, typically two decades higher than available from the single stage open loop amplifier.

Abstract: A photodiode amplifier includes an input stage having a first pair of transistors connected as a differential pair to have a low input impedance and a current source connected into the input stage to bias the pair of transistors. A photodiode is connected into the input stage across the transistors so as to provide differential effect to current flowing through the transistors. By means of such connection, the photodiode is presented with low input impedance, its time constant is accordingly lowered, and the system response of the photodiode amplifier is extended into higher frequencies. The photodiode amplifier is of particular use in an illuminant discriminator capable of distinguishing a range of separate illuminants, including high efficiency fluorescent lighting within the passband of the photodiode amplifier.

Abstract: An optical receiver receives a wideband input signal and separates the wideband input signal into at least a first narrowband signal (FB.sub.1) and a second broadband signal (FB.sub.2). A photodiode (3) receives the wideband input signal and generates a photo-current responsive to the wideband input signal. The photodiode has a first terminal (K) and a second terminal (A). First (1) and second (2) subcircuits respectively are coupled to receive the photo-current generated by the photodiode (3). The first subcircuit (1) includes an amplifier. The first narrowband signal (FB.sub.1) and the second broadband signal (FB.sub.2) are respectively separated from the wideband input signal with the first subcircuit (1) and the second subcircuit (2). The narrowband signal (FB.sub.1) includes a digital (telephone) signal and the broadband signal (FB.sub.2) includes a CATV signal which are both included in the wideband input signal.

Abstract: A receiver is described for optical signals which are amplitude modulated with broadband radio frequency signals. The receiver includes an optical detector which receives the incoming optical signal and generates a radio frequency electrical signal which varies with the power level of the incoming optical signal. This electrical signal is applied to a pair of amplifiers which are connected in a push-pull relationship. A gain control circuit controls the gain of the amplifier pair.

Abstract: The present invention relates to an optical signal input-type amplifier circuit. The object of the invention is to provide an optical signal input-type amplifier circuit which includes a photoelectric converting element with a small light receiving surface, whereby the hf component attenuation in the amplifier can be suppressed and the drive voltage and power consumption can be reduced.

Abstract: An error corrected wide dynamic range amplifier has a transimpedance amplifier where the input signal node is used as a monitoring point for providing an error correction voltage to a combining circuit that also receives the voltage on the output node of the transimpedance amplifier. The combining circuit subtracts the input signal node voltage from the output signal voltage to produce a resultant voltage substantially free of errors produced by non-ideal characteristics of the transimpedance amplifier. The combining circuit may be implemented using analog or digital circuity. The digital combining circuit may also add digital correction values representative of circuit component errors of the wide dynamic range amplifier. Such a wide dynamic range amplifier is usable in high sensitivity, wide dynamic range optical receivers, such as found in optical time domain reflectometers or other optical measurement instruments.

Abstract: An optical parallel receiver according to the present invention is provided with a plurality of photodetectors supplied with light signals, respectively, and a reference photodetector receiving a reference light signal having a constant light power equal to that of the received light signals. The reference photodetector supplies an electric signal to be used for generating a DC reference voltage signal. The DC reference voltage signal is used in all of differential amplifiers, respectively.

Abstract: A wireless binary coded optical data receiver receives the binary encoded data via a photodiode. The binary encoded data is then supplied to the primary winding of a transformer and thus coupled to the secondary winding of the transformer. The secondary winding is coupled to a transimpedance amplifier wherein the transimpedance amplifier buffers the received binary encoded data. The buffered binary encoded data is then amplitude limited by a limiting circuit.

Abstract: A receiver is described for optical signals which are amplitude modulated with broadband radio frequency signals. The receiver includes an optical detector which receives the incoming optical signal and generates a radio frequency electrical signal which varies with the power level of the incoming optical signal. This electrical signal is applied to a pair of amplifiers which are connected in a push-pull relationship. A gain control circuit controls the gain of the amplifier pair.

Abstract: An improved optical receiver for an optical signal amplitude modulated with broadband RF signals is described. The optical receiver includes an optical detector which receives the optical signal and generates a radio frequency electrical signal which varies with the intensity level of the incoming optical signal. The electrical signal is applied antiphased from the optical detector to a pair of cascode transimpedance amplifiers which are coupled in a push-pull relationship. The coupling from the optical detector is matched to each of the inputs of the cascode amplifiers. Bias networks are used for each amplifier to maintain the gain stability of the receiver and to provide better output impedance matching to a coaxial cable for CATV distribution. The optical receiver can provide greater output power for the same input power because of the shared bias currents of the cascode stages in each amplifier.

Abstract: An optical receiver circuit for receiving optical signals is described incorporating a photodetector, two coupling capacitors for coupling each side of the photodetector to respective inputs of a transimpedance amplifier, two current mirror circuits for detecting current on each side of the coupling capacitor and injecting equivalent current to the other side of the other capacitor which is at the input of the transimpedance amplifier, two low pass filters, two current sources and a transimpedance amplifier having two inputs. An optical receiver for receiving optical signals is described incorporating a photodetector having one side coupled to a reference voltage, a current source, a coupling capacitor, a transimpedance amplifier, and a circuit for injecting AC current to the input of the amplifier from the voltage developed across the photodetector.

Abstract: A light signal receiver in which an input of a preamplifier receives a so-called useful electric current output by a light-sensitive device. The preamplifier comprises an input stage having an input transistor assembled with a "common base" whose emitter is connected to the input of the preamplifier and whose base is kept at a fixed potential. A low input impedance and therefore a reduction of the influence of stray capacitance exhibited by the light-sensitive device results from this arrangement Further, a second input transistor can be utilized so that the preamplifier operates as a differential type preamplifier.

Abstract: A system for testing a fiber-optic component with infrared radiation is provided. The testing system has a source of infrared radiation, an optic coupler, a detecting circuit, and an analog tape recorder. The optic coupler directs the infrared radiation onto the fiber-optic component. The detection circuit is electrically connected to the tape recorder. The detection circuit has an amplifier, a potentiometer connected in parallel to the amplifier, and a photoelectric transducer connected in series to the amplifier. These components are mounted on a non-conductive board. A power source supplies voltage and is connected to the amplifier. The circuit operates by having the photoelectric transducer sense the infrared radiation emitted from the tested fiber-optic component and convert the radiation into an electrical signal. The amplifier then amplifies the electrical signal to the voltage necessary for driving the tape recorder.

Abstract: An accurate direct current to 1 MHz (or more) analog information channel with 7.5 kV input to output isolation is provided using a commercially available opto-electronic isolator. The relatively slow response, (limited bandwidth) of the LED portion of the opto-electronic isolator is overcome by providing a frequency compensated negative feedback loop around the servo photodetector in the opto-electronic isolator. The feedback loop includes proper frequency compensation for the phase lag properties of both the LED and the servo photodetector, thus extending the bandwidth well beyond the 200 KHz typical of such opto-electronic isolators.

Abstract: A system for signal level control in AM fiber systems is provided. The system provides level controls at both transmitter and receiver ends of the fiber transmission system, utilizing compensation and control techniques at each end to maintain and optimize the performance of the system. The transmitter includes two stage level control based on a composite power level of a detected RF signal. The receiver includes two stage level control based on a pilot channel filtered from the channels transmitted to the receiver.

Abstract: A receiver circuit for a LAN electro-optical interface includes a high pass filter connected between the optical signal receiving element and the standard ECL line receiver. The high pass filter removes noise from the signal output by the optical signal receiving element, thereby reducing the bit error rate of the system and/or increasing the effective sensitivity of the system, enabling the signal transmission distance to be increased.

Abstract: A receiver is described for optical signals which are amplitude modulated with broadband radio frequency signals. The receiver includes an optical detector which receives the incoming optical signal and generates a radio frequency electrical signal which varies with the power level of the incoming optical signal. This electrical signal is applied to a pair of amplifiers which are connected in a push-pull relationship. In a preferred embodiment, a tuning network is connected between the two amplifiers for optimizing the amplification of a selected band of radio frequencies.

Abstract: An electric-signal amplifying device is provided which includes a light source and an opto-electronic element for amplifying an input signal by use of light emitted from the light source. The opto-electronic element includes a semiconductor substrate and a multi-layered structure disposed thereon. The multi-layered structure has a first semiconductor layer of a first conductivity type, a second semiconductor layer of a second conductivity type, and a third semi-conductor layer of the first conductivity type in this order. The second and third semiconductor layers form a first p-n junction for modulating the amount of light to be absorbed thereinto with a change of bias voltage applied thereto in accordance with the input signal, while the first and second semiconductor layers form a second p-n junction for generating a current as an amplified output signal by absorption of the light transmitted through the first p-n junction.

Abstract: Light Dependent Resistors (LDR's) are used together with a differential amplifier and a plurality of reference resistors to replace conventional analog potentiometer controls and thus offer digital activation and programmability to a traditional style vacuum tube preamplifier.

Abstract: An input stage for an optical receiver with a photodiode (T), which has its output connected, via a capacitor (C.sub.1), to the input of a transimpedance amplifier (f), includes a unit having a resistance depending on the voltage, which is connected between the output of the photodiode and the earth potential of the amplifier. The photodiode is a PIN diode, and said unit with a voltage dependent resistance includes a feed-back amplifier (Df) with a frequency response adapted to that of the transimpedance amplifier.

Abstract: An isolation amplifier employs feedback to accurately amplify an input signal while maintaining electrical isolation between the input and output signals. The isolation amplifier consists of an amplitude modulator, an isolation transformer having a pair of matched secondary windings, a peak-detector output circuit, and a matching peak-detector feedback circuit. The isolation transformer couples an amplitude-modulated signal to both peak detector circuits while maintaining electrical isolation. The output from the feedback circuit is fed back to the amplitude modulator, so that the amplitude-modulated signal represents the difference between the input to the amplifier and the feedback signal.

Abstract: A front end for a broadband optical receiver is disclosed which includes a monolithic integrated Darlington circuit with bipolar transistors (T1, T2). This Darlington circuit is a simple integrated amplifier (OP) developed for UHF application in the range between 0 and 2 GHz. By connecting a suitable transimpedance resistor (R.sub.T) across the Darlington circuit, an improvement in linearity is obtained such that the Darlington circuit can be used together with an avalanche photodiode (APD) in the 0- to 5-GHz frequency range, and together with PIN diodes in short-and medium-length optical tansmission links.

Abstract: Embodiments disclose an adjustable filter (cf voltage-controlled bandwidth) having photoconductors whose resistance is adjusted by variable-intensity radiation source means, with a related feedback loop to compensate for thermal changes.

Abstract: A low-power receiver for extracting a digital data signal from a modulated carrier signal is disclosed. The receiver employs an amplifier whose stages share the same bias current in order to reduce power consumption.

Abstract: An optical receiver includes a photodetecting device and a wide band video amplifier. The photodetecting device and the video amplifier are coupled by reactive elements which are selected to provide a highly linear and highly sensitive response over a frequency range of approximately 400-950 MHz. The crosstalk between two signals are ten parts per billion when the laser power is at 1 milliwatt and modulation is 25 percent per signal. The noise generated by the receiver is only equivalent to 6 billionth of an ampere. The receiver uses commerically available components.

Abstract: An integrated semiconductor device comprising a light emitting portion and a light detecting portion is disclosed. The integrated semiconductor device comprises two multiple quantum well P-I-N structures formed on a single substrate, one of the P-I-N structures being forward biased to emit light and the other of the P-I-N structures being reverse biased to detect light. Because of the quantum confined Stark effect, the reversed biased P-I-N structures is highly absorbing to light emitted by the forward biased P-I-N structure. The integrated semiconductor device may be utilized to implement an optical feedback path for a receiver.

Abstract: A semiconductor light beam position sensor element comprises a semiconductor layer of successively formed p-, i- and n-type semiconductor layers and an electrically conductive layer on either side of the semiconductive layer. At least one of the conductive layers is made of a transparent material, and at least the other conductive layer and the semiconductor layer are provided with a plurality of common apertures extending in the thickness direction. At least one of the conductor layers is provided with one or two pairs of electrodes of opposite polarity and positioned in its marginal regions. The sensor element is light transparent. A feedback circuit is provided to insure that the incident light is constant.

Abstract: An optical receiver incorporating a voltage dependant impedance arranged to shunt excess AC photodetector signal away from the receiver amplifier in response to light level.

Abstract: Embodiments disclose an adjustable filter (cf voltage-controlled bandwidth) having photoconductors whose resistance is adjusted by variable-intensity radiation source means, with a related feedback loop to compensate for thermal changes.

Abstract: An integrating photosensor includes an NPN phototransistor having its collector connected to a source of positive voltage, a P-channel MOS transistor having its gate connected to row-select line, its source connected to the emitter of the phototransistor, and its drain connected to a column sense line. The NPN phototransistor has an intrinsic base-collector capacitance. An integrating sense amplifier according to the present invention includes an amplifying element having an inverting input and a non-inverting input. The non-inverting input is connected to a source of reference voltage the inverting input is connected to a sense line. A P-channel balance transistor is connected between the inverting input and the output of the amplifying element and a capacitor is also connected between the inverting input and output of the amplifying element. An exponential feedback element is connected between the output and the inverting input of the amplifying element.

Abstract: A test apparatus and method is disclosed for determining the absolute noise figure of an optical amplifier. The apparatus comprises an optical receiver and functions to measure the output power of a test noise source, such as a lamp or LED. A plot of input power versus output power yields a linear relationship, with a y-intercept at the test apparatus (first) noise floor (N.sub.0). An optical amplifier to be tested is then inserted in the signal path between the noise source and the receiver. A new plot is generated and a second system noise floor value is determined (N.sub.1). The difference between the two noise floor values (N.sub.1 -N.sub.0) is then defined as the amplifier absolute noise figure (N.sub.A). The inventive technique is equally applicable to semiconductor and fiber optical amplifiers.

Abstract: Where a high bias voltage is required for a photo-element of a photo-receiver, a high voltage is applied to an amplifier which amplifies a photo-current created by the photo-element, when a power supply is turned on. In a prior art photo-receiver, the amplifier may be broken due to this high voltage. In the present invention, the photo-receiver is provided with a protection circuit comprising a diode connected between a power supply circuit and a photo-element, a resistor connected in parallel with the diode, and a first capacitor having one end thereof connected to an anode of the diode and the other end thereof connected to a reference potential. Constants of the circuit components are set such that a time constant of the supply of the power to the amplifier is smaller than a rising time constant of the supply of the power to the photo-element and larger than a falling time constant of the supply of the power to the photo-element.

Abstract: A GaAs MESFET coupled to an interdigited photoconductive detector uses the nternal gain of the interdigited photoconductive conductor and the transconductance of the MESFET to convert an optical control signal to an electrical current control signal which in turn is used to control a GaAs MMIC.

Abstract: The optical receiver includes a photodiode, a preamplifier and a length of transmission line. The photodiode may be connected to the preamplifier, either via the transmission line, or directly between the preamplifier and the transmission line, that is, the transmission line is connected as an open circuit. The transmission line 14 may comprise a coaxial cable, stripline, or any other suitable form of transmission line. The input impedance of the preamplifier should be designed to match the characteristic impedance of the transmission line. The noise of the preamplifier associated with the transmission line has a periodic spectrum dependent upon the length of the line with peaks at odd multiples of f' and minima at even multiples of f'. The value of f' is related to the length of the transmission line in accordance with: f'=v/4L where v is the propagation velocity, typically 2/3 the speed of light, and L is the length of the transmission line.

Abstract: In analog communication, a transmission signal must be demodulated with good linearity. However, linearity of a reception signal is often impaired due to a too large input signal or variations during the manufacture of elements or a fluctuation in power supply voltage. According to this invention, a plurality of source-follower circuits constituting a demodulation circuit are formed on a single semiconductor substrate, a resistor having a high resistance is connected between the gate and the source of a first FET, and another resistor is connected to the source. The gate of each of the second and subsequent FETs is connected to the source of the immediately preceding FET, and its source is connected to the gate of the next FET. A product of a gate width of each of the second and subsequent FETs and a resistance of the resistor connected to the source is set to be equal to that of the first FET.

Abstract: To extend the dynamic range of an optical receiver with a transimpedance amplifier (TIV), it is known to operate the photodiode (PD) as an AC source at high light levels by using a DC-limiting element in the DC circuit of the photodiode, and to convert, by means of an AC circuit, the alternating voltage into an alternating current serving as the input current for the transimpedance amplifier (TIV), which lies within the permissible range. According to the invention, the AC circuit (C.sub.s, R.sub.s) runs from the photodiode terminal (2) not connected to the transimpedance amplifier input to the output (U.sub.a) of the transimpedance amplifier, whereby an extension of the dynamic range is achieved. The current-limiting element is preferably a transistor circuit (R.sub.E, T) connected as a constant-current source.

Abstract: A photoelectric conversion apparatus has a plurality of photoelectric conversion cells. Each cell includes a semiconductor transistor having a control electrode area which in turn includes a plurality of main electrode areas for reading signals. The potential of the control electrode area is controlled to store carriers produced by optical pumping in the control electrode area, to read, from the main electrode area, a signal controlled by the storage voltage produced due to the storage, and to perform a refreshing operation to nullify the carriers stored in the control electrode area. A device is provided for performing a peak detection on the basis of signals from the main electrode area. At least one of the photoelectric conversion cells is shielded from light.

Abstract: A preamplifier for a laser rangefinder receiver having two signal level modes comprises, in accordance with this invention, a light detector having a first load resistor, and a buffer having an input connected across the load resistor and an output to the receiver. A first diode is placed in series with a second diode, with the second diode being connected in parallel with a second load resistor. A positive feedback path is provided from the output to the junction of the first and second diodes, wherein the first and second diodes are nonconductive during a low signal level mode, and conductive during a high signal level mode.

Abstract: A circuit arrangement comprises an amplifier that has an input connected to an opto-electrical transducer and a gain which is controllable with the assistance of a control voltage. In order to achieve a great dynamic range given a constant operating point of the amplifier, the drain-source path of a field effect transistor, a feedback path includes a capacitor, and the input of the amplifier is connected to the output of a comparator that compares the output voltage of the amplifier to a reference voltage. The circuit arrangement can be advantageously employed in optical transmission equipment of PCM technology.

Abstract: The specification discloses an audio signal level control system including a center-tapped photocell incorporated into an attenuator bridge. The cell elements are monitored while processing the audio signal, and a control circuit regulates the light-emitting device in the cell in response to the monitored bridge values. Preferably, log compression and filtering are performed within the control means. Also preferably, a tracking subtraction principle is used in both the audio and control paths to expand the control dynamic range.

Abstract: A substantially zero average DC output voltage is obtained in an instrumentation amplifier without degrading the gain by detecting the output of the amplifier and operating a non-galvanically coupled device responsive to the detected output to apply feedback to the amplifier for balancing out common mode output voltages.

Abstract: A video display system having a forward locking infrared sensor which emits a linear video signal together with a digital graphics generator which generates digital video signals in a plurality of colors; together with a signal video amplifier for amplifying both the linear signal and the high data rate digital signal; the video amplifier having a plurality of curent regulators for regulating the current through a particular resistor where the current regulation is a function of the received linear and digital video signals; the video amplifier also having the capability of current regulation through the resistor in response to variations in the voltage source voltage and thereby eliminating the need for an additional power source voltage regulator.

Abstract: A circuit arrangement has a pre-amplifier that has its input connected to an opto-electric transducer and whose gain is controllable by a final control element formed by a field effect transistor. In order to achieve an especially great range of dynamics, the pre-amplifier contains the drain-source path of a field effect transistor that is connected in parallel to a resistor in a feedback branch. This field effect transistor is activated or inhibited by a regulator. In this way, the range of control of a controllable amplifier arrangement following the pre-amplifier is doubly utilized. The circuit arrangement can be advantageously used in optical transmission equipment of PCM technology.

Abstract: The present invention utilizes a light source mounted on a moving object and providing a light having a constant intensity. A detector circuit creates an electrical detector signal in response to receiving light from a predetermined fixed point of reference. The detector signal is then linearized by a linearization circuit which transforms the detector signal which is substantially nonlinear to a linearization signal which is substantially linear. The linearization signal can then be used in a feedback circuit for causing movement of the moving object, and can be used to precisely control the movement of the moving object.

Abstract: A current mirror circuit 10 is coupled to a first and a second photodetector 18 and 20 and differentially couples together the two photodetectors to an amplifier 12 such that a resulting differential output current is independent of the intrinsic responsivity difference between the two photodetectors. The circuit includes a first transistor 14 having an input terminal coupled to an output terminal of the first photodetector and a second transistor 16 having an input terminal coupled to an output terminal of the second photodetector. A capacitance 22 is coupled between a control terminal of the first transistor and a control terminal of the second transistor, the control terminal of the first transistor further being coupled to the input terminal of the first transistor. A first switch 24 is coupled between the control terminal of the second transistor and the input terminal of the second transistor.

Abstract: The signal-to-noise ratio of a transimpedance operational amplifier is enhanced by employing a large feedback resistor. Bandwidth lost in the process recaptured by a compensation network without reducing the signal-to-noise ratio. The compensation network provides a zero which cancels the upper 3 db pole of the transimpedance amplifier, and also provides a high frequency pole defining the restored bandwidth of amplifier.

Abstract: A field-effect transistor performs four functions, namely signal demodulation, generation of a local oscillator signal, generation of harmonics of this local oscillator signal through frequency multiplication, and mixing of the demodulated signal with either the local oscillator signal or one of its harmonics to produce a signal at a lower intermediate frequency; the field-effect transistor being the key element in a demodulator-downconversion circuit.

Abstract: A radio circuit apparatus for broadcast frequencies promotes micro miniaturization and avoids the production of unwanted radiation by incorporating tunable R-C circuits in place of inductive elements. The apparatus provides simultaneous tuning of RF, mixer, and local oscillator circuits by coupling variable radiation levels to a plurality of radiation-sensitive resistor elements in each circuit. In one configuration of the tuner portion, a rod having a radioactive coating is mounted coaxially within a cylindrical parallel array of resistor elements, the elements being connected in tunable Wien-bridge and/or twin-T circuits. An axially movable, cylindrical shutter is interposed between the rod and the resistor elements for variably blocking the radiation from the rod for tuning the circuits.