Abstract: A passive optical network system having a node that is optically coupled to optical line terminals (OLTs), and that is optically coupled to optical network units (ONUs). The node includes at least one fiber link module (FLM), each FLM including an upstream multiplex conversion device (MCD), and a downstream MCD. The upstream MCD receives an upstream optical signal from the ONUs, converts the upstream optical signal to an upstream electrical signal, and transmits a regenerated upstream optical signal to the OLTs. The downstream MCD receives a downstream optical signal from the OLTs, converts the downstream optical signal to a downstream electrical signal, and transmits a regenerated downstream optical signal to the ONUs.

Abstract: The present invention relates to an inductor (10) for high frequency and high power applications. The inductor (10) comprises at least one wire conductor (20), and a coil zone (30). Windings of the at least one wire conductor comprises the at least one wire conductor being wound around the coil zone to form a substantially torus shape centred around an axis extending in an axial direction of the torus shape. At an outer extent of the coil zone, outer windings of the at least one wire conductor are substantially at a first radial distance from the axis. At an inner extent of the coil zone, inner windings of the at least one wire conductor are substantially at a second radial distance from the axis and substantially at a third radial distance from the axis respectively. When an inner winding of the at least one conductor is at the second radial distance the next inner winding of the at least one conductor is at the third radial distance.

Abstract: A passive optical network system having a node that is optically coupled to optical line terminals (OLTs), and that is optically coupled to optical network units (ONUs). The node includes at least one fiber link module (FLM), each FLM including an upstream multiplex conversion device (MCD), and a downstream MCD. The upstream MCD receives an upstream optical signal from the ONUs, converts the upstream optical signal to an upstream electrical signal, and transmits a regenerated upstream optical signal to the OLTs. The downstream MCD receives a downstream optical signal from the OLTs, converts the downstream optical signal to a downstream electrical signal, and transmits a regenerated downstream optical signal to the ONUs.

Abstract: A distributed amplifier includes a plurality of transistors, a first line connecting gate electrodes of the transistors to each other, and a second line connecting drain electrodes of the transistors to each other, wherein the first line and the second line are electromagnetically coupled to each other at a position situated between immediately adjacent transistors among the plurality of transistors.

Abstract: Overvoltage protection circuitry configured to protect internal integrated circuits within an implantable device in the presence of a high voltage event such as defibrillation or electrocautery. The circuitry allows for an internal node to rise above the voltage level of the high voltage event to insure that an overvoltage protection element is triggered, even if the voltage level of the high voltage event is below the voltage trigger level of the overvoltage protection element.

Abstract: Achievement of robust stability of a power amplifier (PA) that allows the sharing of the ground between the driver stages and the output stage is shown. A controlled amount of negative feedback is used to neutralize the local positive feedback that results from the driver-to-output stage ground sharing in the signal path, for example, a radio frequency (RF) signal path. The solution keeps a strong drive and a good performance of the PA. Exemplary embodiments are shown for the PA positive feedback neutralization. A first embodiment uses a ground signal divider while another embodiment uses a ground signal divider weighting technique.

Abstract: A passive amplifier for use with enhanced power supplies, signal preamplifiers and power amplifiers in communications systems particularly in mobile phones, laptop computers and other battery-powered and battery-limited devices. The passive amplifier can be used as an attachment to electric appliances or other power consuming equipment to significantly reduce the electric power requirements of such equipment. These passive amplifiers do not require an outside source of power and can be used to elevate battery power outputs and serve as either low noise signal preamplifiers or transmit power amplifiers for higher performance and extended battery life. Passive amplifier technology is either electromagnetic or dielectric in nature with component parts limited to inductive, capacitive and resistive components. Dielectric amplifier prototypes have gain values in the range of the 10 dB level so as to be useful in communications applications and power amplification.

Abstract: A feedback resistor is connected between an input terminal and an output terminal of an operational amplifier. A negative resistor is connected between an inverting input terminal and a non-inverting input terminal of the operational amplifier.

Abstract: Conventional single-ended and differential reference buffers used for switched capacitor loads (such as sample-and-hold circuits for analog-to-digital converters) often have errors due to “memory” and are current source limited. Here, however, single-ended and differential reference buffers are provided, which include low bandwidth switched capacitor feedback loops to limit noise from the feedback loop and decouple internal bias nodes to avoid memory issues. Additionally, the differential reference buffers shown include flipped voltage followers that can sink/source large currents, which are not current source limited, and that can be underdamped so as to obtain a two pole settling response to reduce power consumption.

Abstract: Constant and accurate signal gain systems based on controlling oscillator loop gain. A constant gain positive feedback network and an amplifier form an oscillator. Only when the oscillator loop gain is at least one does the oscillator produces an AC signal. Negative feedback of the oscillator's AC signal level is used to keep the loop gain close to or at the value of one by controlling the loop gain of the oscillator circuit. By maintaining the loop gain of the oscillator circuit substantially constant the signal gain is also maintained substantially constant.

Abstract: Systems and methods are provided for controlling headroom of an amplifier (e.g., in a transmitter). A method comprises obtaining a target output power for a current interval and obtaining a target headroom for a subsequent interval. The method continues by adjusting, during the current interval, the power output capability of the amplifier based on the target headroom and adjusting the input power of an input signal based on the target output power, such that the output power of the amplifier is substantially constant during the current interval as the power output capability of the amplifier is adjusted.

Abstract: An improved traveling wave amplifier is disclosed. The improvements to the traveling wave amplifier disclosed include designing the drain-to-drain and gate-to-gate transmission lines as coupled pairs thereby coupling energy back to the input from the output. The result is increased bandwidth without an increase in device count or resorting to a cascade configuration.

Abstract: An audio apparatus is constructed for use in negative drive of a loudspeaker having an internal impedance to perform a desired amplitude-frequency characteristic. In the audio apparatus, an amplifier device drives the loudspeaker with a driving voltage. A feedback device performs a positive feedback of a signal corresponding to the driving voltage of the loudspeaker to the amplifier device with a variable feedback gain, thereby causing the amplifier device to generate a negative impedance effective to negate the internal impedance of the loudspeaker. An adjustment device decreases the variable feedback gain of the feedback device as a level of the driving voltage of the loudspeaker increases, thereby adjusting the amplitude-frequency characteristic of the amplifier device.

Abstract: A circuit for a power amplifier is disclosed which amplifies and outputs an audio signal by amplifying an input audio signal using first and second differential circuits, and driving a push-pull output transistor with the outputs from the first and second differential circuits. The circuit includes a signal generating part generating a disconnection timing signal for disconnecting a bias current reducing activation currents of the first and second differential circuits based on a switch control signal, and positive feedback loops of the first and second differential circuits. A switch part is disposed in each of the positive feedback loops of the first and second differential circuits, disconnecting the positive feedback loops in response to the disconnection timing signal. A bias part stops the operation of the first and second differential circuits by reducing the activation currents of the first and second differential circuits by reduction of the bias currents.

Abstract: A signal processing circuit using positive feedback while keeping the open loop gain of the circuit less than 1 to avoid oscillation. The circuit includes a floating signal source, a low gain amplifier, a feedback element, and a second stage circuit. The floating signal source produces a voltage that is impressed across the feedback element by the feedback system. The feedback element processes the voltage into an output current. The output current is passed through an output current node to the second stage circuit where the output current can be used as a current reference or be further processed. The output from the low gain amplifier may be used as a voltage output node that provides a voltage that is an amplification of the voltage produced by the floating signal source. The signal processing circuit may be embedded in another circuit, including additional stages of the signal processing circuit.

Abstract: An amplifier for high gain, narrowband signal amplification is disclosed. An embodiment is an amplifier including a first means capable of oscillating and a second means for controlling the operating state of the first means between oscillation and close to oscillation. By operating close to oscillator high gain, narrowband signal amplification occurs. By operating between oscillation and close to oscillation, rather than between startup and close to oscillation, the amplifier is always narrowband. Accordingly, an advantage of the invention is operation with minimum affect from interfering.

Abstract: A signal processing circuit using positive feedback while keeping the open loop gain of the circuit less than 1 to avoid oscillation. The circuit includes a floating signal source, a low gain amplifier, a feedback element, and a second stage circuit. The floating signal source produces a voltage that is impressed across the feedback element by the feedback system. The feedback element processes the voltage into an output current. The output current is passed through an output current node to the second stage circuit where the output current can be used as a current reference or be further processed. The output from the low gain amplifier may be used as a voltage output node that provides a voltage that is an amplification of the voltage produced by the floating signal source. The signal processing circuit may be embedded in another circuit, including additional stages of the signal processing circuit.

Abstract: A signal processing circuit using positive feedback while keeping the open loop gain of the circuit less than 1 to avoid oscillation. The circuit includes a floating signal source, a low gain amplifier, a feedback element, and a second stage circuit. The floating signal source produces a voltage that is impressed across the feedback element by the feedback system. The feedback element processes the voltage into an output current. The output current is passed through an output current node to the second stage circuit where the output current can be used as a current reference or be further processed. The output from the low gain amplifier may be used as a voltage output node that provides a voltage that is an amplification of the voltage produced by the floating signal source. The signal processing circuit may be embedded in another circuit, including additional stages of the signal processing circuit.

Abstract: An AC-coupled pre-amplifier is provided for amplifying a signal received in a packet transmitted in burst mode. The pre-amplifier provides a fast time constant for a driven edge of a received signal and a slower time constant for a undriven edge of the received signal. The decay of the undriven edge is faster than the inter-packet time between two received packets. The dual response times, allows for the inter-packet time to be less than the longest string of constant data received in a packet.

Abstract: An oscillator includes an amplifier having an input and an output, and an impedance transformation network connected between the input of the amplifier and the output of the amplifier, wherein the impedance transformation network is configured to provide suitable positive feedback from the output of the amplifier to the input of the amplifier to initiate and sustain an oscillating condition, and wherein the impedance transformation network is configured to protect the input of the amplifier from a destructive feedback signal. One example of the oscillator is a single active element device capable of providing over 70 watts of power at over 70% efficiency. Various control circuits may be employed to match the driving frequency of the oscillator to a plurality of tuning states of the lamp.

Abstract: A cascode amplifier which includes a cascade amplifier stage, an output node (coupled directly or indirectly to the cascode amplifier stage), and positive feedback circuitry coupled between the output node and the cascode amplifier stage (or positive feedforward circuitry coupled between the input node and the cascode amplifier stage) for improved amplifier response to rapidly varying input. Preferably, the amplifier is implemented as an integrated circuit or portion of an integrated circuit, and the feedback or feedforward circuitry is configured to reduce rise times and fall times of the output potential (in response to falling and rising edges of the input) to within acceptable limits, with no more than acceptably small overshoot at both the rising and falling edges of the output potential, and with at least substantially equal overshoot at both the rising and falling edges of the output potential.

Abstract: A capacitively-coupled amplifier circuit includes an amplifier for receiving an input signal via a coupling capacitance and for amplifying the input signal to produce an output signal. A resistor provides a bias voltage to the amplifier. The resistor is bootstrapped using positive feedback with a loop gain of slightly less than one. The bootstrapping causes an increase in the value of the resistor to lower the cut-in (pole) frequency of the amplifier. The bootstrapping or feedback circuit includes a roll-off (pole) at a frequency below the roll-off (pole) frequency of the amplifier. This prevents phase shift in the feedback loop from adversely effecting the high frequency response of the amplifier. The resulting amplifier circuit exhibits a wide passband and excellent low frequency response despite having a capacitively coupled input signal.

Abstract: A temperature compensation circuit used in a negative impedance driving apparatus such as an amplifier for driving a speaker as a load. A current flowing through the load is detected by a detection element connected to the load, and fed back therefrom, so that negative impedance driving is effected on the load. The detection element is set its temperature coefficient to be equal to or slightly larger than a temperature coefficient of the load, thereby the positive feedback gain is changed upon changing the temperature of the load so that negative impedance driving state is compensated. In another aspect of the invention, a temperature sensitive element or temperature detecting element for sensing or detecting the temperature of the detection element is arranged to change the positive feedback gain and compensate the negative impedance driving state.

Abstract: An FM receiver is self tested by connecting a positive feedback network in circuit with a wideband, front end r.f. amplifier of the receiver, so that the amplifier is converted into an oscillator. R.f. and i.f. characteristics of the receiver are determined by comparing the amplitude of an i.f. signal with a predetermined reference value while the amplifier is converted to an oscillator. Noise characteristics of the receiver are determined by comparing the amplitude of an audio frequency signal of the receiver with a predetermined value while the amplifier is converted to an oscillator and the amplifier derives an unmodulated r.f. output. Baseband characteristics of the receiver are determined by varying a reactance in the positive feedback path to impose FM on r.f. oscillations derived by the amplifier and by comparing the amplitude of the output of the audio frequency amplifier with a predetermined value.

Abstract: A method and apparatus are disclosed for regulating the operation of a TWT. The TWT regulation is achieved by detecting the operating condition of the TWT, e.g., by measuring dynamic gain, and regulating feedback of the TWT output in response to the TWT operating condition. The invention is preferably implemented so as to augment the TWT input drive from an exciter source to induce the TWT to drive itself into saturation. The inventive technique comprises determining whether the TWT is operating in a desired operating condition, e.g., saturation, feeding back to the TWT input a portion of the TWT output power to the TWT input, and regulating the feedback signal to keep the TWT operating in the desired condition. Determination of whether the TWT is operating in a saturation condition may be affected through measurement of the TWT dynamic gain. The invention permits dynamic management of the feedback to accommodate variations in gain of the TWT, e.g.

Abstract: An MOS sampling comparator circuit including a differential amplifier for producing first and second amplified signals, a first positive feedback circuit for further amplifying the first amplified signal, a second positive feedback circuit for further amplifying the second amplified signal, a strobed latch, having a positive feedback circuit, for further amplifying and storing the signals from the first and second positive feedback circuits, and a circuit for outputting complementary logic signals in response to the latched signals. By providing the first and second positive feedback circuits, small analog differential voltage input signals to the differential amplifier are further amplified and coupled without delay to the latch, resulting in an accurate conversion of the analog input signals to logic signals at high speed.

Abstract: A Metal-Oxide Semiconductor (MOS) high gain amplifying stage which overcomes the inherently low transconductance, gm, of MOS transistors is described. This is achieved by using a specially configured load transistor in combination with a driver transistor. The load transistor is provided, by means of positive feedback, with a current generator which is dependent on the output voltage of the stage and has an effective negative output conductance. The positive feedback is achieved by connecting an appropriate attenuation stage between the output and the input of the load transistor. By the cancellation of output conductances between the driver and load transistors, a near infinite voltage gain can be achieved despite resistive loading at the output of the amplifier. The MOS amplifying stage has application in amplifiers, comparators and oscillators.

Abstract: A three-stage amplifier circuit specially configured to provide a high input impedance. An initial emitter follower transistor stage amplifies the current level of an ac input signal to produce a first intermediate signal, a common-base transistor stage amplifies the voltage level of the first intermediate signal to produce a second intermediate signal, and a final emitter-follower transistor stage amplifies the current level of the second intermediate signal to produce an output signal in phase with the input signal. A feedback circuit feeds back the output signal to the input of the common-base transistor stage, to supplement the first intermediate signal input. This effectively increases the input impedance of the common-base transistor stage and, likewise, the initial emitter follower transistor stage, whereby the amplifier circuit can be used to amplify signals produced by high impedance sources.

Abstract: An improved differential amplifier includes two Darlington transistor pairs (44-45, 46-47) connected to form a Darlington differential amplifier having complementary sides. Two cross-coupling transistors (50, 52) connect thereto for providing complementary positive feedback of gain less than one between the sides. The cross-coupling transistors significantly improve the differential gain and differential input resistance of the Darlington amplifier.

Abstract: An audio amplifier having an auxiliary terminal for connection of a feedback line to the grounded terminal of a loudspeaker and including a circuit for protection against voltage overload on the amplifier and loudspeaker if the auxiliary terminal is inadvertently connected to the ungrounded terminal of the loudspeaker, or in case of malfunction of the feedback circuit. The protection circuit includes a signal generator activated by the closing of a power switch for circuiting a check signal through the terminals of the loudspeaker to the auxiliary terminal and a controller sensitive to the voltage at the auxiliary terminal for controlling a switch for muting the output of the amplifier if the voltage at the auxiliary terminal exceed a predetermined value.

Abstract: A positive feedback RC active biquadratic filter circuit comprising a passive input RC section and an active amplification output section having at least one operational amplifier. The RC section has two true resistive T-networks and a true capacitive T-network connected to receive an input signal. The RC section realizes a second order function with a low Q factor. The operational amplifier has a feedback resistive connection from an output thereof to a mid-junction point between each of three capacitances in the capacitive T-network. The capacitive T-network and one of the two resistive T-networks are connected to a positive input of the operational amplifier. The other resistive T-network is connected to a negative input of the operational amplifier.

Abstract: In a high-fidelity sound reproducing system wherein the speaker is located remotely from the amplifier and therefore the electrical signals reaching the speaker are subject to distortion from the capacitive and inductive reactance of the conductors joining the amplifier to the speaker, and further subject to pickup of hum and other forms of interference, the distortion of the signal is substantially eliminated by the use of a negative feedback network connected between the input terminal of the load and the input terminal of the amplifier and by a positive feedback network connected between the input terminal of the amplifier and the return terminal of the load, the feedback loops operating on the amplifier to alter its output in such a way that the signal applied at the terminals of the remote speaker more nearly resembles the signal applied as an output to the amplifier.

Abstract: The suspension of movable system instruments, for example, a galvanometer, introduces elastic reset torques upon deflection. To compensate for such torques and render the apparatus essentially independent of the deflection torques, an opto-electronic device provides an output signal representative of the deflection which is combined with the deflection voltage applied to the galvanometer to at least in part compensate for the reset torque introduced by the moving system suspension.

Abstract: Circuits are disclosed for normalizing a device which has a current-controlled frequency response, such as a YIG or a TWM device, to a predetermined current-frequency (I-F) characteristic in order that a device equipped with such a circuit can be preadjusted for substitution in a system for a like device without realigning the system. The normalizing circuit is in parallel with the device, and is comprised of a transistor and a compensating current-sensing resistor in series with the transistor. A shunt compensating current, I.sub.C, through the transistor is set by a voltage on a potentiometer to offset the I-F characteristic of the composite device and circuit from that of the device to a predetermined level and also by a feedback control circuit connected to the compensating current-sensing resistor. The slope of the offset characteristic is then adjusted to a predetermined value by adjusting the gain of a feedback control circuit between the transistor and a resistor which senses a voltage, V.sub.

Abstract: An apparatus and method for improving the bass response characteristics of an electrodynamic loudspeaker is described. The loudspeaker normally exhibits actual mechanical parameters such as damping, compliance, and mass which normally determine the bass response and lower cut-off frequency of the loudspeaker. The method and apparatus of the present invention cause the loudspeaker to exhibit apparent mechanical parameters which differ from the actual mechanical parameters to substantially change the effect of the actual mechanical parameters on the bass response. The apparatus in a preferred embodiment includes an electrical network through which electrical energy corresponding to the sound to be reproduced is applied to the voice-coil of the loudspeaker. The electrical network has an effective output impedance including a negative impedance in series with a plurality of impedances connected in parallel.

Abstract: A transconductance amplifier circuit including two operational amplifiers, as shown in the accompanying drawing, is disclosed. The gain of the amplifier circuit is determined by the resistances R1, R2, R3 and R4. The scale factor relating the output current i.sub.out to the input voltage e.sub.in is determined by the setting of the switches S1, S2, and S3, which adjust the amount of resistance between the output current terminal I.sub.o and the output terminal of the second operational amplifier A2. For R1/R2 = 1; R3/R4 = 1; and switch S1 closed i.sub.out = e.sub.in /R5. This transconductance amplifier circuit provides common mode rejection between the input voltage and the output current.

Abstract: A differential amplifier is arranged to amplify faithfully the voltage produced by an ungrounded voltage source to provide the amplified result as a voltage in relation to a reference (ground) voltage. Errors resulting from leakage resistances between the ungrounded voltage source and ground are avoided by providing an inverting amplifier responsive to the output voltage, which draws, through a resistance, a current from a terminal of the voltage source which is proportional to the output voltage of the differential amplifier. This causes a shift of the potential of the voltage source in the direction towards the reference voltage. Optimum results are obtained when the shift is such that the variations in the voltage source being observed are caused to become balanced in relation to the reference potential.

Abstract: A circuit permitting an operator to accurately calibrate an instrument to indicate when a variable analog quantity being measured is zero. The analog signal is connected to the input of an operational amplifier which operates in stable mode for large analog inputs and operates in oscillation mode for very small analog inputs. The output of the operational amplifier is compared to zero and when the analog input is greater than zero, the comparator output is a logic zero. When the analog input is less than zero and not in the immediate vicinity of zero, the comparator output is a logic one. When the analog input is very small and less than zero, the operational amplifier operates in oscillation mode as the circuitry connected thereto causes it to oscillate with the duty cycle of the negative portion of the oscillation decreasing as the analog input comes closer to zero. Accordingly, the output of the comparator also oscillates.

Abstract: A circuit for receiving low transmission voltage, direct current data signals is described. The circuit operates to form the received signal into two voltages which are symmetrical with respect to ground, and the latter two voltages are coupled to the inputs of a difference amplifier. The amplifier comprises two, oppositely-phased outputs which are coupled to different ones of the inputs. An amplified differential signal is produced at a third output terminal.

Abstract: A booster circuit for a liquid crystal display device of a timepiece is disclosed. The booster circuit is a sort of a blocking oscillator having a transformer of which turns ratio is 1 : n (where n is a real number). The rectified output voltage of said blocking oscillator is superposed on the voltage of the cell so that the output voltage of the booster circuit is higher than of the blocking oscillator. A smoothing condenser has ample capacitance to have a larger time constant than the fluctuation time of the voltage of the cell owing to mechanical shock.