Abstract: A configurable feedback path is included in an amplitude control system having a signal source and an amplitude controller, and provides accurate tracking between a signal provided at a test port and a reference signal, whether or not the configurable feedback path is in an internally-leveled configuration or an externally-leveled configuration. The configurable feedback path includes a series of access ports, a detector that has an input coupled to the first access port, a filtered output coupled to the amplitude controller, and an unfiltered output providing the reference signal. The configurable feedback path also includes a signal separator that has an input terminal coupled to the signal source, a thru-terminal coupled to the third access port, and a coupled terminal that is coupled to the second access port. The fourth access port is coupled to the test port.

Abstract: The present invention discloses an impedance matching circuit which is suitable to be applied on an IC chip. The impedance matching circuit comprises a resistor unit, an OP amplifier circuit connected with the resistor unit, a feedback selecting circuit connected in parallel with the OP amplifier circuit, and a resistor selecting circuit connected with both the OP amplifier circuit and the feedback selecting circuit. The feedback selecting circuit further includes a plurality of switching circuits for enabling some of the resistors furnished in the resistor selecting circuit. By selecting and actuating one of the switching circuits, some certain resistors will be enabled so as to adjust the resistance value of the resistor selecting circuit. The resistor unit and the switching circuits are designed in such a manner that the resistor unit is able to compensate an equivalent resistance of the switching circuit which is actuated.

Abstract: A method and device to emulate impedances includes a pair of impedances connected in series between two circuit nodes, the impedances forming a voltage divider having at its midpoint a reference voltage VX. An OP AMP includes a positive input connected to the VX—node and the negative input connected to the output thereof in a direct feedback loop. The OP AMP output is also connected to a load impedance that is connected either one of the nodes. A transistor may be interposed between the load impedance and the circuit node. The OP AMP may be provided with a negative gain to emulate an inductor. The voltage divider may be variable to emulate a variable impedance.

Abstract: An electronic amplifier providing very low distortion which includes an output stage with an output error correction stage containing two amplifiers and wherein there are at least four local negative feedback paths, an output of the first amplifier being connected to an input of output stage transistor buffers or output stage transistors through a first network, an output of the second amplifier being connected to an input of output stage transistor buffers or output stage transistors through a second network, where components of the first and second amplifier the local negative feedback paths, first and second networks and output stage transistor buffers are selected to form substantially second order local dominant pole. Also disclosed is the supply of power to said first and second amplifiers from a floating power supply means coupled to either an or the output of the output stage so that the voltage of the floating power supply will follow substantially an output voltage of the output stage.

Abstract: A line driver combining active impedance and filter in one stage for connection to a transmission line having a characteristic impedance. The line driver comprises an amplifier, a transformer with a primary to secondary winding ratio of 1:n, a reference impedance, an input impedance and two feedback impedances. The primary winding of the transformer has a first end connected to the output of the amplifier and the secondary winding is connectable to the transmission line. The reference resistor has an end connected to the second end of the first winding at a junction node and the feedback circuit is connected to the input and output of the amplifier and also to the junction node. The reference impedance has a value equal to n 2 K times the characteristic impedance of the transmission line.

Abstract: The invention relates to a device for amplifying electronic signals, including: an amplifier PRA, and a plurality of feedback loops G1, G2 placed between the output and the input of the amplifier, which feedback loops are arranged so that each feedback loop has an adjustable gain and all the feedback loops jointly form an assembly having an equivalent impedance which is substantially independent of the gain settings selected. Thanks to the invention, the amplification bandwidth can be easily adjusted without adversely affecting the performance of the device in terms of noise and high cut-off frequency.

Abstract: A synthetic impedance line driver for driving a telecommunication line includes a complementary operational amplifier pair having cross-coupled positive feedback summing resistors. The driver circuit is configured to provide a relatively large multiplication of the values of relatively small valued output resistors to realize a synthesized impedance matching that of the driven line. A cross-coupled resistor network may be employed to cancel out far end signal components present in an analog canceler drive signal. The values of the auxiliary network resistors are ratioed such that the signal at nodes between resistors of branches of the network is a fraction of the open circuit voltage swing of the amplifiers, with far end signal components canceled.

Abstract: A method and device to emulate impedances includes a pair of impedances connected in series between a supply voltage and ground, the impedances forming a voltage divider having at its midpoint a reference voltage Vx. An OP AMP includes a positive input connected to the Vx node and the negative input connected to the output thereof in a direct feedback loop. The OP AMP output is also connected to a load impedance that is connected either to the supply voltage or ground. The unity gain OP AMP forces the output voltage thereof to follow the input voltage Vx, whereby the output voltage behaves as if it were created by a virtual impedance. By proper choice of components and values, the virtual impedance may comprise a large capacitor, and the remaining impedances may comprise resistance and small capacitance, both of which, together with the OP AMP, are easily integrated in a small die area.

Abstract: An apparatus is disclosed for processing an input signal. The apparatus includes two feedback loops for generating output signal components from the input signal. Each loop contains an oscillator, which has a frequency or phase which is variable in response to a control signal, and a comparator for generating the control signal. The oscillator generates a loop output signal which forms one of the components of the output signal. The apparatus also includes a combiner for combining the loop output signals to produce the output signal. For each loop, the apparatus also produces a feedback loop operating signal, these signals being dependent on the output signal and in phase quadrature with one another. One input of the comparator in each loop receives the feedback loop operating signal, and the other input of the comparator receives a component of the input signal.

Abstract: A line driver with positive feedback reduces the output signal amplitude excursion required for driving a communication line, and enables the driver's output impedance to be synthesized using a reduced component value, thereby achieving a reduction in power loss through the output resistor, while simultaneously matching the effective electrical value of the driver's output impedance to the line. The line driver includes an operational amplifier having differential polarity inputs and an output. An output resistor, whose value is a fraction of the line impedance, is coupled between the amplifier output and an output node coupled to the line. A negative feedback resistor is coupled between the amplifier output and an inverting input. A further resistor is coupled between the amplifier output and a non-inverting input.

Abstract: A two stage operational amplifier circuit comprises a first stage (31) having an input (2, 4) and an output, and a second stage (33) having an input and an output (19). The second stage input is coupled to receive the first stage output. A feedback path (41, 45, 47, 51) is coupled between the output and the input of the second stage. The feedback path (41, 45, 47, 51) comprises a low-frequency compensation path (41, 45) and high-frequency compensation path (45, 47, 51). The feedback path (41, 45, 47, 51) is compensated such that the frequency response of the second output of the second stage is substantially 6 dB per octave throughout the high-frequency region.

Abstract: A dual band filter network for a radio communication apparatus is provided. The network has an antenna (212) for receiving and transmitting signals from a first frequency band and a second frequency band. The network has a first duplex pair (202) including a first transmit filter (204) including a first passband and stopband. The first duplex pair (202) also includes a second receive filter (206). The first filter (204) presents a consistent phase in the second passband due to the wide frequency separation between the first filter (204) and the second filter (206). The network has a second duplex pair (202') with similar characteristics as the first duplex pair (202). The network also has a switching circuitry (210) controlled by a switch control voltage (214) for selecting the appropriate filter circuitry. The network can be provided in a small sized, low cost package that also offers improved insertion loss performance.

Abstract: A highly efficient linear amplifier and/or modulator and demodulator comprising first and second feedback loops is provided. Each loop processes a component of the input signal and the component signals are recombined at, for example, a summing junction 18. The feedback signals for each loop are dependent upon the output signal and are in phase quadrature. The input signal is separated into I and Q signals, which are also in phase quadrature, by a component separator 10.

Abstract: In a method and by an apparatus for correction of error signals and for forming of an arbitrary transfer function being independent of the quality of a payload (loudspeaker; H1) included in a signal amplification system, a control system (9) is used for supplying of the input signal to a basic amplifier (1) driving the payload. Said control unit includes a further amplifier (9) having an inverted input being supplied with a feedback signal from the output of the basic amplifier. In such a case the further amplifier involves only an inverted input, said input signal is supplied through one (4) of the resistors (3, 4) included in the feedback loop.

Abstract: A family of wideband amplifier circuits using series and shunt feedback over two stages to achieve constant impedance, including single-ended, single-ended input/differential output and differential input/differential output forms.

Abstract: The invention features power amplifying apparatus with controllable frequency characteristic of the gain. The apparatus includes a band pass network of two cascaded amplifiers and multiple resistors and capacitors arranged to form multiple feedback loops. The feedback loops stabilize the output A.C. signals and establish a predetermined bandwidth of the network. The apparatus also includes a capacitor resistor feedback loop, connected to the output of the second amplifier and input of the first amplifier, with the capacitor and the resistor selected to maximize the loop gain at a desired frequency.

Abstract: Negative-feedback amplifier provided with an active amplifier section operating approximately as a nullor and a negative feedback section, the amplifier having a high loop gain. The active amplifier section is constructed in balanced form with two nullors connected in balance, and the negative-feedback section is composed of passive impedances and comprises two negative-feedback loops. In one embodiment each nullor has a series-coupling circuit and a parallel-coupling circuit at the input port. As a result an accurately defined or characteristic input impedance is obtained, and a series- or parallel-coupling circuit is formed in both negative-feedback loops at the output port, so that a high (current output) or low (voltage output) output impedance, respectively is obtained. In another embodiment each nullor has a series-coupling circuit and a parallel-coupling circuit at the output port.

Abstract: A feedback amplifier for providing an amplified signal to first and second utilization networks includes first and second feedback paths. The amplifier output is coupled via a first coupling resistor to a first terminal to which the first utilization network is connected, and via a second coupling resistor to a second terminal to which the second utilization network is subject to being connected. The first feedback path couples the amplifier output to the amplifier input exclusive of the first coupling resistor. The second feedback path couples the amplifier output to the amplifier input and includes the second coupling resistor. The amplifier output signal remains substantially constant in the presence or absence of said second utilization network.

Abstract: Feedforward of the source signal into the compensation mode of an operational amplifier produces more than an order of magnitude improvement in small-signal capability at high frequencies. The technique is useful for active filters and wideband amplifiers. Further improvement will be available using amplifiers designed for this approach.

Abstract: A nonlinear distortion synthesizer having an amplifier and one or more over-threshold power-function negative-feedback paths. Each negative-feedback path provides a feedback signal which is separately adjustable for each signal polarity. The feedback signal for each polarity is proportional to a power function of the portion of the output signal which exceeds a predetermined threshold.

Abstract: A broadband microwave recursive filter that provides sharp transitions in the frequency domain between adjacent stop and passbands comprising a signal input node; a signal output node; a filter circuit connected between the signal input node and the signal output node for providing a signal flow therebetween which has a predetermined frequency bandwidth characteristic; a microwave transistor circuit, with the microwave transistor circuit being band-limited to provide gain in only a restricted window of frequencies within the predetermined frequency bandwidth and connected for providing amplification to signals flowing in the filter circuit between the signal input node and the signal output node while suppressing out-of-window signals resulting from design approximations.

Abstract: The invention includes a simple and inexpensive thermal controller and simple and inexpensive radio frequency alternating current generator which are provided in an improved temperature control system for a resistively heated electrochemical cell. The temperature controller is formed by a single amplifier with feedback circuit which provides the function of a combined deviation amplifier and two mode (percent proportional band and integral functions) controller. The alternating current generator uses a single direct current voltage source to generate a radio frequency alternating electric current. The two elements are combined in a temperature control circuit for a resistively heated electrochemical cell. The control circuit provides an alternating current with varying power by cyclicly shutting the current off for irregular portions of a predetermined cycle period.

Abstract: An active filter includes a first active stage including an operational amplifier and feedback means wherein the non-inverting input terminal of the operational amplifier is at a ground potential; a second active stage configured in the form of Miller integrator using an operational amplifier and connected in series with the first active stage; and means connecting the non-inverting terminal of the operational amplifier of the second active stage to the inverting terminal of the operational amplifier of the first active stage for enhancing the filter characteristics.

Abstract: In a signal amplifying apparatus which is provided with a amplifier, a feedback circuit having its input connected via a CR circuit to the output of the amplifier and its output connected to the input of the amplifier, a first terminal connected with the output of the amplifier for connection with a first cord connected with the input of a load, and a second terminal connected with the input of the feedback circuit for connection with a second cord connected with the input of the load, there are provided means for detecting whether the second cord is connected with the second terminal, and connecting means for connecting the output of the amplifier directly to the input of the feedback circuit by the detected output from the detecting means without passing through the CR circuit.

Abstract: A modulated carrier signal, the amplitude variations of which are smaller than the amplitude of the unmodulated carrier, is not very suitable for transmission over radio links because the required use of non-linear components, such as class-C amplifiers, result in an unwanted widening of the transmitted spectrum. According to the invention an arrangement for amplifying such a signal comprises two oscillators (16, 17) the desired relative phase of which is adjusted in a loop including a control circuit 22. On combining the oscillator signals v'.sub.k and v'.sub.g, there is produced a resulting signal r which is a replica of the input signal v having the amplitude variations. As the oscillators 16 and 17 produce signals having a constant amplitude, these signals can be easily amplified, for example by class-C amplifiers.

Abstract: The herein-described broadcast apparatus for controlling the loudness level of program signals includes a variable gain device for increasing or decreasing the level of incoming program material as a function of program loudness while simultaneously holding the output level below a preset level to assure proper modulation levels and/or to prevent excessive reaction by peak limiters which usually follow the loudness controller in the broadcast chain.

Abstract: A wide-band direct-current coupled transistor amplifier is provided which exhibits uniform gain in a frequency range from direct-current to greater than 100 MHz, and which exhibits other desirable features.

Abstract: A feedback system for a multi-stage amplifier is disclosed which includes a nest of feedback loops centered on a particular stage, for example, on the output stage. This enables a very large amount of feedback to be applied to that stage, and enables constant return difference to be obtained for that stage over a nominated frequency range. Bode's limits for mid-band loop-gain magnitude and its rate of attenuation with frequency can be exceeded.

Abstract: Improved slew recovery in a composite driving amplifier for driving a substantially reactive load including a feedback loop to the operational amplifier from the load for regulating the output of the amplifier, the composite amplifier has a predetermined resistance R1 in the feedback loop and includes a second feedback loop having a predetermined resistance R2. The second feedback loop extends from the output of the operational amplifier to the negative input and is substantially parallel with the first-mentioned feedback loop. To maximize the recovery of the amplifier from a slew condition, the relationship of R1-R2 should be as follows: ##EQU1## wherein: V.sub.o is the output voltage in the amplifier.Slope, is the slope of the load voltage curve during the overload condition, andDelay represents the period of time it takes the overload operational amplifier to respond to a feedback signal at a given overload condition.

Abstract: The circuitry is arranged to develop a highly accurate and stable reference electric level voltage and/or current for distribution to a plurality of logical circuits on a semiconductor chip having of the order of a thousand such circuits thereon. An input reference voltage is developed by a source reference circuit and applied to an operational amplifier circuit having "evener" circuitry for substantially equalizing the currents in the input transistors. This evener circuitry is essentially an operational amplifier within an op-amp. It monitors and adjusts feedback voltages. The operational amplifier and evener circuitry drives a reference voltage distribution grid laid out over the semiconductor chip.

Abstract: A nonlinearly variable gain circuit is utilized to produce an inverted logarithmic S curve of gain versus potentiometer rotation while using a linear resistance taper potentiometer. An operational amplifier feedback circuit uses the linear potentiometer and a resistance network in combination.

Abstract: A feedback resistor is interposed between a reversing input terminal of an audio amplifier and at least one impedance circuit. The impedance circuit is connected to an output terminal of the amplifier to receive an amplified audio signal from the amplifier. The signal controlled in its frequency characteristic in the impedance circuit. A fraction of the signal is negatively fed back to the amplifier through a feedback resistor.

Abstract: A variable filter circuit, especially for synthesizing and shaping tone signals, in which a variable light source is provided which influences light sensitive resistor elements in the filter circuit. The variable circuit, by the use of selector switches, can provide different musical features, such as muted voices, percussion, brass, woodwind and the like, all of which will enhance, for example, existing organ voicing while it is, furthermore, possible to obtain the effect of playing a solo instrument together with organ voicing.

Abstract: A self biasing low input impedance differential amplifier for current mode applications requiring wide bandwidth with response down to DC. A shunt-shunt differential mode feedback system in combination with a series-shunt common mode feedback system is connected between an input amplifier stage and an output amplifier stage. An additional shunt-series common mode feedback signal is applied to the input stage to short out the common mode component of the amplifier input signal and minimize input signal drift. High open loop gain in the differential feedback loop provides low impedance amplifier inputs.

Abstract: In order to realize a precision variable equalizer of little errors by a simple circuit arrangement, a plurality of variable transmission circuits having variable transfer coefficients are connected in series between input and output terminals, and feed-back and feed-forward are applied from input and output sides of the respective variable transmission circuits to input and output portions of the variable equalizer through transmission networks having specified transfer characteristics.

Abstract: An electronic filter circuit having controlled "Q" with variations in attenuation. A plurality of filter networks are connected in parallel between the output and the input of an amplifier in a manner such as to be capable of selectively providing negative feedback to the amplifier. Each filter network includes inductive, capacitive and resistive elements, with a potentiometer forming part of the resistance thereof. Each potentiometer is connected in series with a resistor having the same value thereas, the arm of the potentiometer being connected to its associated filter network such that the "cut" to which the potentiometer is set determines the total value of the resistance presented by the filter network in the feedback circuit. The potentiometers and associated resistors are each connected in series with each other, these series connected elements being connected in parallel between the input and the output of a unity gain amplifier.

Abstract: The input stage of an amplifier circuit formed from first and second semiconductor differential amplifiers comprising a pair of transistors having emitter electrodes connected to each other, respectively. The respective collector electrodes of one pair of transistors in each of the first and second semiconductor differential amplifiers is connected to the respective collector electrodes of the other pair of transistors, the base electrode of one transistor of each pair of transistors respectively being connected to an input terminal of the amplifier circuit and the base electrode of the other transistor of each pair of transistors respectively being connected to first and second negative feedback circuits connected to the output stage of the amplification circuit. First and second electrical switches are respectively connected to the common emitter electrodes of each pair of transistors. One of the first and second electrical switches is controlled to be closed selectively.

Abstract: An amplifier circuit, comprising a capacitive-resistive network electrically connected between the input and output of the amplifier wherein the network provides equivalent capacitance between the input and output thereby providing frequency response compensation.

Abstract: An amplifier circuit having a variable transmission factor and an effective transmission frequency band delimited by a lower limit frequency is arranged to enable the value of the lower limit frequency to be varied as a function of a control voltage, by including in the circuit an amplifier member and circuit components defining a feedback path connected between the output of the amplifier and an input thereof which is inverting with respect to the output signals of the amplifier, the components defining the feedback path including an electronically voltage-controllable resistor having a control voltage input and a first frequency dependent impedance connected in parallel with the resistor, and the circuit further including a second frequency dependent impedance connected between the inverting input of the amplifier and a point at the circuit reference potential, and a line for supplying the control voltage to the control voltage input of the controllable resistor.

Abstract: A system for controlling the application of heat energy to a ceramic exhaust gas sensor and for linearizing the output signal from the sensor. The system compares, electrically, the resistance of a conductive heater winding against a fixed reference and permits a flow of electrical current through the heater whenever the comparison indicates that the temperature of the heater is below the desired level. By periodically establishing a flow of electrical energy through the heater and terminating that flow whenever the heater temperature reaches the desired level, the temperature of the heater may be held at the desired level with great accuracy. In order to periodically reestablish the flow of electrical energy through the heater, the system further provides an oscillator arranged to reestablish current flow through the heater a fixed time period following termination of current flow through the heater.

Abstract: A single adjustable control is commonly connected with each of a plurality of feedback channels, which are selectively coupled in an amplifier circuit to provide the latter with different basic gains, to adjust the respective basic gains of the amplifier circuit by corresponding fractional or proportional amounts of respective ranges of permissible gain chain for each channel, thereby simultaneously to correct or to calibrate each channel for different amounts of drift of the like.

Abstract: A zeroing circuit for use in conjunction with devices that produce output signals in response to input data signals feeds a compensating signal into such a device to produce a zero output signal when there is a zero input signal. The device being compensated is intermittently tested for the zero condition, and an aspect of the compensating signal is altered to produce the zero condition.

Abstract: A low-noise, stage-stabilized, direct-coupled, single-ended amplifier cirt is disclosed which has a unique feedback network combined therewith in such manner that degenerative alternating current and substantially constant direct current feedback signals are supplied thereto, so as to effect an exceptionally steady amplification factor therefor over a very broad frequency response band.

Abstract: An amplifier circuit whose gain bears a desired relation to a control voltage, including a differential amplifier, a plurality of impedances interconnected between the amplifier terminals and switches interconnected with the impedances and switchable between two states which create two impedance configurations that give the circuit mutually complementary gain vs. control voltage control characteristics.

Abstract: A device is provided for controlling the sensitivity of a receiver of the type comprising a photosensitive element operative to convert radiant energy into electric signals and having an amplifier connected to the output of the photosensitive element and signal processing members for separating a useful signal from interfering background radiation. A sensor device is connected to the photosensitive element to sense the direct current which the element emits in response to radiation from the sun or other strong sources of disturbance, the sensor device being operative to emit a signal when the direct current exceeds a predetermined value, and a switching device responsive to said signal operates to switch the amplifier from a given fixed sensitivity level to a lower fixed level of sensitivity.

Abstract: A signal frequency band control system comprises an amplifier for amplifying an input signal. A first differentiation or integration circuit receives an output signal from the amplifier and carries out a primary differentiation or primary integration. A second differentiation or integration circuit is supplied with an output signal from the amplifier and carries out a secondary differentiation or secondary integration. A first gain constant circuit multiplies the output signal from the second differentiation or integration circuit by a first gain constant. A second constant circuit multiplies, by a second gain constant, the signal resulting from the addition of the output signal of the first differentiation or integration circuit and the output signal of the first gain constant circuit. A circuit negatively feeds back, to the amplifier, a signal resulting from the addition of the output signal of the amplifier and the output signal of the second gain constant circuit.

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: Current and voltage feedback are used in separate frequency dependent major loops around a high gain broadband amplifier to produce frequency shaped gain and matched input and output impedances.

Abstract: A distortion-free amplifier for electric signals has a high-quality low-power amplifier-section. In addition there is a high-power amplifier-section which delivers the majority of the current to the load. A feedback signal is derived which is a measure of the output current of the high-power section and not the low-power section. The feedback signal is applied to the inputs of both amplifier-sections negatively in an amount such as to remove from the combined output currents in the load any distortion occurring in the contribution from the high-power section.

Abstract: An operational amplifier-type active filter in which the only capacitor in the circuit is the compensating capacitance of the operational amplifiers, the various feedback and coupling elements being essentially solely resistive.