Abstract: An amplifier includes an output buffer having an input coupled to a gain node which is the common node of the outputs of first and second current mirrors for receiving a signal current and having an output for providing an amplified drive current. The output buffer includes a first transistor of a first type having its base coupled to a gain node of the output buffer and to the base of a first transistor of a second type for receiving the signal current. The emitter of the first transistor of a first type is coupled to the base of a second transistor of a second type. The emitter of the first transistor of the second type is coupled to the base of a second transistor of the first type. The emitter of the second transistor of the first type is coupled to the emitter of the second transistor of the second type and to the output of the buffer.

Abstract: A current feedback amplifier having circuitry in its input stage for matching the error current created due to a parasitic capacitance (C.sub.IN) on the negative, or inverting input terminal (V.sub.IN-). Additional circuitry in the input stage subtracts the matching current from the error current created by C.sub.IN to cancel the error current due to C.sub.IN and thus eliminate the peaking of gain at high frequencies caused by C.sub.IN. In addition to cancellation of C.sub.IN errors, the subtraction process in the input stage enables cancellation of error current resulting from bias current common mode rejection (ICMR) as well as component dissimilarities created during processing.

Abstract: An amplifier with controlled output impedance utilizing current and voltage feedback to set gain and output impedance is disclosed. The voltage feedback is provided by feedback resistor connected from the output to the inverting input. The current feedback is provided by feeding a current proportional to the output current directly to the inverting input of the amplifier. An error amplifier is used to maintain the proper ratio of the current feedback to the output current and to cancel the effects of the output device impedance on the overall output impedance. Two such amplifiers driven by complimentary signals form a differential amplifier with controlled output impedance. Because the output impedance is a function of the voltage feedback resistance and the current feedback ratio, it is possible to digitally control the output impedance by changing the feedback resistance and/or the current feedback ratio.

Abstract: A capacitance compensation circuit for a current feedback amplifier which compensates for error current created due to a parasitic capacitance C.sub.IN on the negative, or inverting input terminal V.sub.IN. The capacitance compensation circuit includes a capacitor C* connected to the positive input terminal V.sub.IN+ utilized to couple current from V.sub.IN+ to the collectors of emitter follower transistors having bases coupled to V.sub.IN+ and emitters connected to V.sub.IN-.

Abstract: An IC amplifier having first and second cascaded stages formed by respective pairs of symmetrical complementary bipolar transistors followed by a unity gain buffer amplifier and provided with overall current feedback. The quiescent collector currents of the second amplifier stage are controlled by respective transconductance generators with respective complementary bipolar transistors connected in parallel relationship to the transistors of the second stage. The collector currents of the transconductance generators are fixed at the levels of respective reference current generators.

Abstract: A circuit for regulating the charging time of the output node of an amplifier at start up. The output node commonly comprises an external soft-start capacitor charged by a current delivered by a pull-up transistor of a push-pull output stage of the amplifier, through a decoupling diode that is functionally connected between the output node of the amplifier and a terminal of the external soft-start capacitor. The present application provides a current mirror feed back circuit capable of mirroring the charge current of the external soft-start capacitor onto the driving node of the pull-up transistor of the output stage of the amplifier. The regulating circuit permits use of an external capacitance of extremely small size. Upon the reaching of a fully charged condition by the external capacitor, the control circuit self-isolates and does not influence in any way the normal operation of the amplifier.

Abstract: A bipolar micro-power rail-to-rail operational amplifier has a low complexity output stage that provides a high ratio of load current to no load idle current. The output stage includes first and second output transistors of opposite conductivities whose current circuits are connected in series at the output terminal between high and low voltage supplies. A control transistor responds to the drive voltage at its base by modulating the base-emitter voltages of the first output transistor and a gain transistor in opposite directions to modulate their respective output and gain currents. A regenerative current source supplies current to the gain transistor by returning the gain current in a regenerative feedback loop to its emitter so that the current source idles at a low gain current but is capable of supplying much higher gain currents.

Abstract: A bipolar micro-power rail-to-rail operational amplifier has a low complexity output stage that provides a high ratio of load current to no load idle current. The output stage includes first and second output transistors of opposite conductivities whose current circuits are connected in series at the output terminal between high and low voltage supplies. A control transistor responds to the drive voltage at its base by modulating the base-emitter voltages of the first output transistor and a gain transistor in opposite directions to modulate their respective output and gain currents. A regenerative current source supplies current to the gain transistor by returning the gain current in a regenerative feedback loop to its emitter so that the current source idles at a low gain current but is capable of supplying much higher gain currents.

Abstract: An operational amplifier includes a pair of current mirror circuits and a buffer circuit commonly connected to outputs of the pair of current mirror circuits and a first current source. The first current source is electrically connected to the current mirror circuits so as to be controlled by operating currents of the current mirror circuits.

Abstract: At high frequencies, a video amplifier draws a higher current and normally is biased to provide such current. However, since high frequencies are rarely encountered, the present circuit controls the operating point as a function of the frequency. More specifically, a controlled variable which controls the operating point of the amplifier stage is obtained in dependence on the frequency to which the amplifier stage is driven.

Abstract: An amplifier circuit with a stabilized bias in its output stage includes a push-pull type output-circuit having a first transistor and second transistor connected to each other in Darlington connection, a third transistor and a fourth transistor respectively operating complementarily with the first transistor and the second transistor. The third transistor and fourth transistor are connected to each other in Darlington connection, and the second transistor and fourth transistor are connected in series as output stage transistors between terminals of a DC power supply source.

Abstract: An amplifier output stage that can be operated with low supply voltages and as a voltage amplification greater than one has two complementary transconductance amplifiers having asymmetrical characteristics of their output currents with reference to the input voltages. The amplifier output stage also has two power amplifiers following these transconductance amplifiers and whose outputs are connected to the output node of the amplifier output stage. The amplifier output stage also has a feedback network that is connected between the output node and a reference potential node and defines a feedback node that is connected to respectively one of the inputs of the transconductance amplifiers, whereas the other inputs of the transconductance amplifiers are connected to the input node of the amplifier output stage.

Abstract: A scheme is presented for offsetting varactor error currents that are coupled to the gain nodes of amplifier circuits through transistors having their collectors connected to these gain nodes. For each vatactor error current generating transistor, a compensating diode circuit is connected so as to replicate the vatactor error current, and the replicated current is coupled to the gain node to offset the vatactor error current of the corresponding transistor. In order to replicate the vatactor error current of a given transistor, each compensating diode circuit comprises a diode for which the capacitance and the voltage dependence thereof substantially track those of the collector-base junction of the corresponding transistor. The voltage driving the vatactor error current in the transistor is coupled to one electrode of the compensating diode, the other electrode of which is connected to the emitter of the transistor having its collector connected to the gain node.

Abstract: A current feedback amplifier having circuitry in its input stage for matching the error current created due to a parasitic capacitance (C.sub.IN) on the negative, or inverting input terminal (V.sub.IN-). Additional circuitry in the input stage subtracts the matching current from the error current created by C.sub.IN to cancel the error current due to C.sub.IN and thus eliminate the peaking of gain at high frequencies caused by C.sub.IN. In addition to cancellation of C.sub.IN errors, the subtraction process in the input stage enables cancellation of error current resulting from bias current common mode rejection (ICMR) as well as component dissimilarities created during processing.

Abstract: First and second current feedback transconductance amplifiers (102,104) each have a high impedance voltage input, a low impedance current input and a pair of push-pull current outputs. In a single-ended configuration, an input signal is applied to the voltage input of the first transconductance amplifier (102) and the push-pull outputs of the both transconductance amplifiers are connected through a current mirror (136,138) to a node (134) where the current outputs are summed. The node current is integrated by a capacitor (174) to produce a voltage which is amplified by a transimpedance amplifier (190) to produce an output voltage which is fed back to the voltage input of the second transconductance amplifier (104). The current inputs of the transconductance amplifiers (102,104) are interconnected by a resistor (132). The high impedance voltage inputs produce common-mode cancellation of distortion in the transconductance amplifiers (102,104) and low input shot noise.

Abstract: An amplification circuit includes a push-pull type output circuit including first and second output transistors operating complimentarily connected in series between dc current source terminals, the bases of the first and second transistors being driven by a pre-stage output, a current detecting resistance inserted between either one of the first and second transistors and the dc current source terminals for detecting a bias current of the output circuit, an error amplification circuit for amplifying difference between voltage across the current detecting resistance and reference voltage and for negative-feedback controlling the bias current of the output circuit, and a diode connected in parallel to the current detecting resistance for bypassing a current flowing during outputting of a signal.

Abstract: An amplifier stage suitable for current conveyors and current mode feedback operational amplifiers has low input resistance and operates at low power. The amplifier stage comprises a buffer having inverting and non-inverting inputs and a pair of current outputs, and a pair of multiple output current mirrors which operate in conjunction with the buffer to generate an output current at a high gain node in response to an input signal applied to the buffer inputs. Each multiple output current mirror has a low impedance current input for receiving current signals generated by the buffer and multiple high impedance current outputs for providing current feedback to the inverting input of the buffer and output current to the high gain node of the amplifier stage. The magnitudes of the feedback and output currents are determined by the resistances of current scaling resistors associated with the low impedance current input and each of the high impedance current outputs.

Abstract: A current feedback operational amplifier input stage is provided that uses a pair of dual output current mirrors to couple current from the inverting input of the amplifier to the high gain node of the amplifier, and to reduce the input impedance of the inverting input by means of local current feedback. Each of the dual output current mirrors employs an emitter degenerated Wilson-type current mirror in conjunction with an emitter degenerated transistor current source to detect signal current at the inverting input and use this current to control the bias current at both the inverting input and the high impedance node of the amplifier. The ratio of bias currents in the dual output current mirrors are controlled by scaling the resistances of the emitter degeneration resistors corresponding to each current node.

Abstract: A bipolar power supply capable of selectably supplying either a positive or a negative voltage at an output terminal. The power supply comprises a first operational amplifier, a second operational amplifier, a first transistor electrically connected to a positive voltage source and a second transistor electrically connected to a negative voltage source. The first transistor is electrically connected to the first operational amplifier and the second transistor is electrically connected to the second operational amplifier so that the first and second amplifiers control the operation of the first and second transistors respectively. The inputs of the first and second operational amplifiers are electrically connected in a manner that prevents them from simultaneously providing large positive voltages at their outputs.

Abstract: A circuit for increasing the slew rate of linear amplifier circuits. The circuit comprises two NPN and PNP transistor pairs arranged so that when the voltage level difference between the amplifier output and input voltage exceeds the base to emitter voltage of such transistors, the circuit is activated. The circuit provides a current proportional to such voltage difference in order to speed up the charging or discharging of the slew rate determining capacitance.

Abstract: An amplifier which combines the low quiescent current requirements of a Class B transistor amplifier with the minimal distortion qualities of a Class AB amplifier. In one disclosed embodiment the amplifier is utilized as a receiver amplifier and as a transmitter in a modular telephone adapter for coupling a telephone headset to a conventional modular telephone comprising a handset and a base unit. Signal expansion circuitry takes advantage of the dynamic emitter resistance of transistors in the amplifier's output stage through modulation of collector current in the output transistors and inverted phase summation of the resulting error signal with the input signal. DC bias circuitry supplies a current supply which is relatively insensitive to changes in power supply or device parameters.

Abstract: An amplifier device comprises an amplifier circuit, a differential amplifier for amplifying the difference between an input and an output of the amplifier circuit with an amplification degree which is substantially equal to one, and an addition circuit for adding an input signal to an output signal of the differential amplifier circuit and applying the result of addition to the input terminal of the amplifier circuit. Thereby, the distortion of the amplifier circuit is eliminated, and the input signal and the output signal coincide with each other. Hence, by applying the technical concept of the invention to an amplifier with a feedback loop, the distortion factor can be reduced without the increasing of the amount of feedback.

Abstract: A current feedback circuit for controlling the error current in current feedback amplifier includes transistor biasing circuitry which monitors the error current to detect high input signal slew rates and switches on a transistor controlled shunt circuit to divert drive current from the transistors forming the amplifier input, when the error current generated exceeds a threshold value.

Abstract: An amplifier arrangement suitable for use as a line driver is built with a Class AB stage connected in parallel with a Class B stage, whereby the output currents of the stages are summed. Each of the Class AB and the Class B stages has an output current device that is connected in a common-source configuration.In a push-pull configuration of the arrangement, each of a pair of operational amplifiers in the Class AB stage separately drives each of a pair of operational amplifiers in the Class B stage.

Abstract: A negative feedback amplifier including, in an input stage, a common-emitter first transistor and a common-base second transistor for supplying a quiescent collector current (standing current) to the first transistor so that a sufficient standing current flows. A negative feedback circuit is connected between an output terminal of an output stage and the emitter of the second transistor, and a first limiter diode is parallely connected to the feedback circuit so as to prevent saturation of an NPN transistor of the output stage. The common-base transistor in the input stage makes it possible to select a high resistance resistor as a feedback resistor, thus enabling the standing current of the output stage to be reduced. A second limiter diode may be connected between the output terminal and the input terminal of the output stage.

Abstract: A transconductance generator including a cross-coupled quad circuit having first and second pairs of complementary transistors, wherein one of the first pair is in series with a complementary one of the second pair, and the other two transistors also are in series. Two input terminals are provided, one for each pair of cross-quad transistors. Two current mirrors are provided, one being coupled to a set of two NPN cross-quad transistors, and the other coupled to the two PNP cross-quad transistors. The cross-quad circuit and the current mirrors provide an output signal through a pair of output transistors. By connecting the output signal to the second input terminal, negative feedback is developed to provide a unity-gain buffer. A number of special compensating circuits are provided to assure minimum distortion effects in the output signal.

Abstract: An operational amplifier having input and output stages with positive capacitive feedback to the output stage derived from a point in the circuit where the voltage is proportional to the output voltage.

Abstract: An electrical circuit for amplifying complex, wideband signals, preferably audio and servo/robotic signals, comprises a first input buffer in an emitter-follower configuration or in a source-follower configuration. A bias current rail traverses the first buffer. The low impedance output of the first buffer is connected to a load resistor, preferably in the order of 50-500 ohms. The circuit further comprises positive and negative opposing current mirrors connected to the bias current rail that reflect the currents created in the bias current rail by an input voltage signal imposed across the load resister. The combined outputs of the current mirrors are connected to the input of a second buffer. The output of the second buffer is connected via a feedback means to the output of the first buffer and to a load. The first buffer is driven by dual voltage supply rails, preferably a lower voltage, in the order of 15 Volts.

Abstract: An amplifier circuit includes a negative feedback connected amplifier and a series circuit comprising a capacitor, one end of which is connected to an output terminal of the amplifier, and a resistor, one end of which is connectable to a reference potential. A comparator is provided which has first and second inputs and one output. The first input is connected to a junction between the capacitor and the resistor, the second input is connected to an output of the amplifier, and the output of the comparator is connected to one input of the amplifier. The comparator does not react to an AC signal of a specific frequency band, but operates to set the output offset voltage only to one fractional part of the transition gain, and therefore operates to accomplish offset compensation without using a large capacitor.

Abstract: A single-ended amplifier circuit is provided combining high speed operation with low input offset characteristics while providing immunity from power supply noise for the input signal by isolating the power supply conductors from the input conductor. The first and second amplifying transistors are separated from the power supply conductors by the drain-source conduction paths of third and fourth isolation transistors operating in their linear region in response to a predetermined reference potential. Thus, any power supply noise is absorbed across the third and fourth isolation transistors thereby avoiding overwhelming a low level input signal with switching induced noise.

Abstract: An audio amplifier reduces crossover distortion typical of class AB push-pull amplifiers by including means for preventing either of the output transistors from being cut off during any portion of the audio waveform. This desirably eliminates sharp discontinuities associated with the transfer function of the amplifier. The circuit includes two base-emitter voltage multipliers and a nonlinear transconductance feedback amplifier.

Abstract: An amplifier having an input stage with inverting and non-inverting input terminals, a voltage amplifier stage with relay terminals and being operatively connected to the input stage, a SEPP output stage with transistors and an output terminal, and a constant-current bias circuit between the relay terminals for absorbing current bypassing between the relay terminals. The transistors are connected to the output terminal via resistors. The constant-current bias circuit is free of being in direct connection with the output terminal. The amplifier is incorporated in place of an emitter follower in a compact disc player or laser video player and may be incorporated into a driver of a loudspeaker, a magneto-optical recording system or a magnetic disc system for mass storage.

Abstract: An amplifier output stage with minimum circuitry and optimum performance for providing a SAT-to-SAT output voltage signal at an output terminal. The amplifier output stage includes a first transistor having a collector coupled to the output terminal for sourcing current thereto, a base coupled to a first supply voltage terminal, and an emitter coupled to the first supply voltage terminal. A second transistor having a collector coupled to the output terminal for sinking current thereat, a base, and an emitter coupled to a second supply voltage terminal. A third transistor having a collector, a base coupled to the base of the second transistor, and an emitter coupled to the second supply voltage terminal by a first resistor. A fourth transistor having a collector coupled to the first supply voltage terminal, a base coupled to an input terminal, and an emitter coupled to the base of the third transistor.

Abstract: A high current drive integrated circuit amplifier in which the quiescent currents in the output transistors are controlled by control current signals which are applied to respective input signal amplifiers and which are of values determined by currents flowing in respective current sensing transistors associated with the output transistors. The control arrangement ensures that the output transistors can not be driven to a non-conducting condition.

Abstract: A low impedance class AB buffer stage in complementary transistor technology has its quiescient current stabilized and its operation thereby made more reliable by means of suitable error op-amps that are supplied with transistor feedback loops which are connected to the stage's output terminal through resistors. In addition, for full rail-to-rail output voltage capability, transistor switching devices are added to turn off current through either of the resistors when the output voltage approaches the voltage of either power rail, and also a pair of serially rail-to-rail connected transistor is connected in parallel with the feedback loops.

Abstract: In an amplifier comprising an input stage having an inverting input terminal and a non-inverting input terminal, a voltage amplifier stage operatively connected to said input stage, and a SEPP output stage including first and second control ends connected to first and second relay output terminals of said voltage amplifier stage respectively, it is characterized by comprising a constant-current bias (CCB) circuit connected between the first and second relay output terminals so as to absorb the current bypassing between said relay output terminals. The first CCB circuit is connected in parallel to a so called constant-voltage bias circuit whose internal resistance has been increased as compared with that in the conventional CVB circuit so that most portion of the bias current borne by the CVB circuit is shared by the present CCB circuit.

Abstract: A bridge-type linear amplifier includes separate local feedback networks on each half-side channel of the amplifier and an additional feedback network between channels of the amplifier in order to correct for differences in current gains of output transistors and requisite drive currents.

Abstract: A wideband integrated circuit amplifier includes a pair of current mirror circuits sensing emitter currents of NPN and PNP transistors in the amplifier output stage. A pair of current mirror circuits divide the emitter currents, respectively, by a factor of 20. The current mirror output currents are summed, current splitter directs approximately 1/20 of the summed mirror currents through a transistor, the collector of which is coupled to the gate electrode of a field effect input transistor of a bias control circuit, to produce a scaled down feedback current. A high impedance current source is connected to the collector of the transistor. The bias circuit adjusts the DC bias voltage applied between the base electrodes of the transistors to cause the scaled down feedback current to equal the constant current. A very small compensation capacitor produces a low frequency pole that prevents the bias circuit from interfering with high frequency performance characteristics of a wide band amplifier.

Abstract: An amplifier includes two differential amplifiers which are connected to an output stage comprising two field effect transistors of opposite conductivity typed directly coupled in series between opposite poles of a DC voltage source. The junction between the two output transistors constitutes the output of the amplifier. A negative feedback loop connects the amplifier's output to the inputs of the differential amplifiers. A correction arrangement is provided to prevent excessive current consumption and cross-over distortion. Preferably, the correction arrangement uses a pair of current mirror circuits to generate respective measuring currents proportional to the current in each of the output transistors. Each such measuring current is compared with a reference current.

Abstract: This amplifier stage has saturation control and high dynamics. The stage comprises a pair of input current sources connected in series between a pair of reference voltage lines, a pair of output transistors, connected between the pair of reference voltage lines and defining an intermediate output terminal and a driving circuit comprising active elements and interposed between the input current sources and the output transistors.

Abstract: In a wide-band direct-coupled transistor amplifier, the current through the power output stage must be stabilized to prevent fluctuations in the amplifier output signal. To stabilize the output stage current, a negative feedback loop is established providing a bias control for the amplifier input stage. In the past, voltage feedback apparatus, typically including operational amplifiers, has been utilized. In the present invention, a current feedback path, which avoids the voltage level translation inherent in the prior art, is used to provide the feedback bias control for the input stage of the amplifier. A technique for the compensation of temperature drift and for voltage offset is described.

Abstract: A high speed buffer circuit is composed of complementary symmetry emitter follower driver and output stages. The input of driver stage includes active load devices cross-coupled to the output stage inputs so that the output stage is bootstrap driven from emitter followers. The circuit is biased by level shifting means to operate as a class AB current amplifier. It displays a wide bandwidth along with a high slew rate and can source or sink a large pulsed current.

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

Abstract: A broadband amplifier comprising insulated collector vertical pnp transistors, a circuit device effective to improve frequency response, and a final stage comprising a so-called complementary pair formed of an npn transistor and a pnp transistor having emitters connected to each other and to an epitaxial layer n of the insulated collector vertical pnp transistor incorporated in the gain circuit of said amplifiers. The complementary pair afford minimization of the junction parasitic capacitances of the aforesaid vertical pnp transistor.

Abstract: The disclosed amplifier comprises a MOSFET output stage biased for Class A operation and a bipolar current amplification stage biased for Class C operation. The latter stage is normally cut off, and at low power output levels the entire output signal current is provided by the output stage. Current sensing resistors measure the magnitude of the output current and apply to the base-emitter junctions of the current amplification transistors a bias voltage proportional to the output current. When this current reaches a predetermined magnitude the current amplification stage becomes active so as to provide additional output signal current in parallel with that provided by the output stage. As a result at higher power output levels the output stage sees a load impedance much higher than that of the loudspeaker system and therefore has a flatter load-line which maintains its operating point in the active region.

Abstract: A class B push-pull integrated circuit suitable for low voltage operation, having two symmetrical halves. Each half circuit has first and second opposite conductivity type transistors having their collectors connected together to the base of a class B driver transistor, the collector of which drives the base of an output transistor. An AC input signal is divided into in-phase and anti-phase components one of which is applied to the base of each first transistor. An AC feedback loop extends from the collector of the fourth transistor through a voltage divider and level shifter to the base of the second transistor. A DC feedback loop extends from the base of the fourth transistor through a fifth transistor to the base of the second transistor. Decoupling capacitors extend from the bases of the fifth transistors and through a diode to ground. The arrangement allows use of small decoupling capacitors, and a current forced through the diode eliminates turn-on delay.

Abstract: An audio power amplifier employs highly linear power MOSFET gain circuitry that uses distortion cancellation rather than negative feedback to maintain high linearity and to greatly reduce transient intermodulation distortion.

Abstract: Errors occurring in the beam current measurement in a video output stage can be reduced by increasing the recharging rate of the capacitive load of a video amplifier, constituted by the picture display tube of a picture display arrangement, with the aid of a bias current or a quiescent current which is subtracted again from the current applied to an input of the beam current measuring circuit which is controlled by the video amplifier.

Abstract: The distortion of an emitter-follower output stage of a video amplifier for driving a cathode of a picture display tube can be reduced without rendering a beam current control via this output stage impossible, by using a low-distortion buffer stage for producing a negative feedback signal at the output of the output stage. A higher follow rate for small signal variations can be obtained with the aid of a bias current or quiescent current which then is subtracted again from the current applied to an input of a beam measuring circuit which is controlled by the output stage.

Abstract: The telephone amplifier of an audio transmission circuit comprises a class-B output stage as a result of which the required supply current of this amplifier is considerably lower than with prior art telephone amplifiers. A distorting voltage produced by the current signal in the supply current of the glass-B output stage does not affect the output signal of the telephone amplifier because the input stage and the output stage each comprise their own setting circuits which produce mutually independent setting voltages.