Abstract: A measuring amplifier device is provided with an input circuit producing different functions of an input signal in order to permit output signals in different measuring ranges to be produced. The circuit can be constituted by an operational amplifier having a feedback connection composed of a series arrangement of several elements each defining a particular measuring range together with subtraction stages forming signals corresponding to each range, or by a plurality of diodes or diode-resistor networks connected to divide the input signal between them and each defining a different measuring scale.

Abstract: Circuitry for compensating for the effects of changes in ambient temperature on an automatic gain control arrangement in a missile-borne receiver is shown to include an operational amplifier responsive only to the level of the output signal from an automatic gain detector and amplifier, such end being effected by using temperature sensitive elements in the input and feedback circuits of the operational amplifier.

Abstract: An improved fast-recovery circuit for ECG amplifiers and the like. The fast-recovery circuit includes threshold responsive circuitry connected in parallel with part of the resistance associated with the integrator in a feedback circuit of the amplifier. The threshold responsive circuitry operates to increase feedback frequency response of the integrator when the normally very low frequency output signal of the amplifier exceeds a certain threshold. The improved circuit prevents the threshold circuitry from responding to pulses or excursions in the output signal of a relatively higher frequency content and which exceed the amplitude threshold for less than a predetermined interval, as for instance caused by pacer spikes, large QRS complexes and the like. Preferably, the improved threshold responsive means comprises transistor means connected across the integrator's resistance and having capacitance means across the base-emitter circuit thereof for inhibiting response to certain short duration signals.

Abstract: A non-linear direct-current amplifier in particular for linearizing the output characteristic of a measuring transducer, comprising a main amplifier of which the overall gain is determined by means of one or more non-linear operational amplifier elements of which the individual outputs are connected by way of respective summing resistors with the input of the main amplifier, the input of each operational amplifier element being connected with the tapping of a resistive voltage divider connected between the output of the main amplifier and a reference potential source. Depending on the construction and connection of the operational amplifier elements, amplifier characteristics having increasing, decreasing or both types of slopes can be approximated by rectilinear sections.

Abstract: A circuit for selecting a clipping level including a passive clipping element having a transfer function like that of either a zener diode, two series connected opposing zener diodes or other passive clipping elements. An inverting operational amplifier with a selectable gain couples to the passive clipping element and by adjusting the amplifier gain, the clipping level can be selectively reduced to almost zero from that of the clipping level for the passive clipping element itself.

Abstract: The gain of an operational amplifier is switched between +K dB and -K dB by switching circuit positions of the input and feedback impedances. The gain is changed in 0.1 dB steps by changing either the input or feedback impedance by a ratio of 1.0116 for each step. The gain is changed in 1.0 dB steps by changing the other of the feedback or input impedance by a ratio of 1.122 for each step. A novel two-pole switching arrangement employs the foregoing techniques to permit unambiguous gain polarity changes.

Abstract: An electronic echo apparatus comprising an input amplifier, an output amplifier connected thereto through a transmission channel, a delay device connected in parallel to said channel, and a feedback path connected in parallel to said delay device, characterized in that said feedback path includes a control means, and in that there is connected to the output of the output amplifier a means for measuring the output signal of said output amplifier, comparing said output signal to a predetermined threshold value and, when said output signal reaches said threshold value, supplying a control signal to said control means for terminating the feedback.

Abstract: The circuit includes a signal path extending between an information signal input terminal and an information signal output terminal. A differential amplifier, having a non-inverting input and an inverting input, is included in the signal path, and a feedback path, containing electronically controlled impedance, connects the amplifier inverting input to the amplifier output. A branch path is branched off from the information signal output terminal and, in this branch path, a control voltage is derived from the information signal and fed to the electronically controllable impedance. In accordance with the invention, the information signal input terminal is connected to the non-inverting amplifier input to feed the information signal thereto. Two diodes are connected in parallel with each other, but in oppositely poled relation, across the feedback circuit, to limit the feedback voltage between the amplifier output and the amplifier inverting input.

Abstract: The collector current of a first transistor serves as the base drive current for a second transistor of opposite conductivity type than the first transistor. When conduction occurs through the collector-to-emitter path of the second transistor, a conducting diode connected between the emitter of the first transistor and the collector of the second transistor clamps this collector to a relatively fixed voltage level referenced to the fixed base voltage of the first transistor. This prevents saturation of the second transistor and thus reduces the "storage delay", that is the turn-off time delay of the second transistor. In addition, the charge stored at the base electrode of the second transistor is removed when its collector-to-emitter current flow is interrupted to further reduce the turn-off time of this transistor.

Abstract: An amplifier whose transmission factor is to be controlled as a function of a control voltage and including an amplifier member having a negating input, connected to have its impedance varied by the control voltage and an electronically controllable variable impedance having one side connected to the amplifier member output, a second impedance connected between the other side of the first impedance and ground, and a switch assembly for switching the connections within the amplifier between two operating states providing mutually complementary control characteristics, the amplifier member output providing the amplifier output in one operating state and being connected to the negating input in the other operating state, and the point of connection between the impedances being connected to the negating input in the one operating state and providing the amplifier output in the other operating state.

Abstract: The invention covers an amplifier circuit in which the output is limited in either polarity. Normally, a part of the output voltage is fed back to the input to maintain linearity but when the output reaches a maximum or minimum value, any further departure is amplified and fed back to the input circuit to neutralize the part of input signals which is outside of the range to be amplified. The feedback amplifier can be designed to initiate limiting at any desired output voltages and the positive and negative output limit voltages can be asymmetric with respect to the quiescent output voltage.

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 switching circuit comprises an operational amplifier with two resistive negative feedback paths including respective unilaterally conducting devices (e.g. diodes) connected in opposite polarity to the output of the amplifier. A first terminal is connected to the electrode of the unilaterally conducting device in one path remote from the output of the amplifier, and a second terminal is connected to the electrode of the unilaterally conducting device in the other path remote from the output of the amplifier. Signals of one polarity only applied to the first terminal appear at the second terminal and signals of the opposite polarity only applied to the second terminal appear at the first terminal. The circuit may include three or more such feedback paths. The values of the resistors in the feedback paths may be adjusted to charge the transfer gain of the circuit.

Abstract: A voltage controlled variable gain circuit comprising: first, second, third and fourth same polarity transistors for dividing the output current of a first operational amplifier by dc gain control voltage and being connected with the output terminal of the first operational amplifier to which an input signal is applied; means for driving in inverse phase the respective pairs of a first and third transistors, and a second and fourth transistors; a first feedback circuit including a second operational amplifier with an inverting input terminal connected with the output terminal of the first transistor, a first resistor element and a first PN junction element connected in series between the input and output terminals of the second operational amplifier, and a second resistor element and a second PN junction element connected in series between the output of the second operational amplifier and the input terminal of the first operational amplifier, so as to negatively feedback the output current of the first trans

Abstract: A condition responsive element, disclosed as a negative temperature coefficient thermistor, operates in conjunction with a bridge circuit to provide a differential input to a special direct current amplifier system. The amplifier system utilizes a combination of positive feedback and negative feedback with the negative feedback always exceeding the level of the positive feedback under steady state operating conditions. The output of the amplifier means further is connected to the lowest energizing potential for the amplifier means through a network that includes a relatively fixed voltage dropping means so that changes in the negative feedback can be made to change the gain of the amplifier system with a minimum of offset or change in calibration of the condition responsive device.

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: 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: An electrical isolator has a transformer with an impedance in series with the primary winding and a high gain amplifier amplifying voltages induced in the secondary winding. Feedback is provided from the amplifier output to produce a current generating flux in the transformer core in opposition to flux produced by current in the primary. Thus the flux density is reduced and with a very high gain amplifier may be made close to zero and well away from saturation.

Abstract: A communications receiver transversal filter equalizer is disclosed of the type using fixed increment tap weight adjustments involving use of amplitude data from the incoming signal in conjunction with tap weight adjustments.

Abstract: An output stage and feedback circuit for a buffer amplifier are disclosed. The output stage protects an operational-amplifier circuit preceding it from overvoltages appearing at the load. The circuit includes a pair of complementary transistors in a push-pull arrangement that sources and sinks current to and from the load. Both the transistors are in common-emitter configurations, and each one has a corresponding diode connected between its collector and the load in an orientation opposite that of the collector-base junction. The diodes prevent the reverse current that would otherwise flow in response to an output overvoltage of the polarity that forward biases the collector-base junction of the transistor, and the over-voltage is thereby prevented from being seen at the operational-amplifier output terminal. Overvoltages of the other polarity are not seen because they reverse bias the base-collector junction.

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 capacitance magnification circuit comprising an amplifier having a positive gain G, a first capacitor having a value C1, and a second capacitor having a value C2. The first capacitor is connected between the input port of the amplifier and an input port of the circuit, the second capacitor is connected between the input and output ports of the amplifier, and the output port of the amplifier is connected to an output port of the circuit. An effective capacitance value C1.sup.2 /.delta. is realized when the condition (G-1)C2-C1=.delta. is satisfied, where .delta. is an arbitrarily small positive value.

Abstract: Symmetrical push-pull power amplifier employing a pair of complementary output transistors having their collectors connected to an output terminal. The output transistors are each driven by an associated input transistor of the opposite conductivity type. Feedback diodes are coupled between the collector of each output transistor and the input of the input transistor associated with the other output transistor. A feedback diode is forward biased while the output transistor to which it is coupled is conducting, thus biasing to nonconduction the input transistor to which it is coupled. Therefore, when the polarity of the input signal to the input transistors changes, the output transistor that is off is not turned on until the output transistor that is on has dissipated the charge stored therein and is not conducting.

Abstract: A measuring circuit including a piezoelectric transducer contains an output charge amplifier circuit with a semiconductor element connected across the storage element of the charge amplifier. The semiconductor element controls the resetting or zeroing of the storage element to thereby effect control of the operation of the charge amplifier. Typically, the semiconductor element may be a field effect transistor, photo-device, etc., and the control of the same may be remotely controlled.

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 high-frequency automatic gain control circuit for a common emitter earthed amplifier wherein a hybrid negative feedback is applied to an input stage thereof from the emitter of an output stage transistor through a hybrid transformer connected to the base of an input stage transistor and a series negative feedback is applied to the output stage thereof, and according to the present invention a diode which is shunted by a capacitor is connected in series to an emitter resistor of the output stage transistor, and an automatic gain control signal is applied to said diode for regulating the gain of said amplifier by controlling negative feedback ratio of said negative feedback.

Abstract: An amplifier is disclosed which may selectively be connected to different input circuits and which is provided with a plurality of switchable negative feedback impedance networks. A feedback attenuation impedance is provided which prevents oscillation of the amplifier triggered by positive feedback through switch leakage resistance between switch contacts. The attenuation impedance lower the loop again in the circuit formed by the amplifier, leakage resistance and disconnected feedback impedance by lowering the loop gain below the oscillation point.

Abstract: A feedback circuit for feeding back the output voltage of a comparing amplifier to the input circuit of the comparing amplifier for causing a steep change in the output voltage so as to stabilize the operation of the succeeding circuit. The feedback circuit includes means for applying the feedback voltage to a low potential portion of the input circuit of the comparing amplifier.