Abstract: A CMOS translator which includes an amplifier having an input node and an output node; a first clamp for providing a clamped feedback signal from the output node to the input node of the amplifier; and a second clamp for providing a clamped feedforward signal from the input node to the output of the amplifier. ECL signals are translated up to CMOS voltage levels with high speed, low power consumption via a circuit with requires minimal die area. The unique clamping arrangement provides a self-biasing feature which affords a large error margin.

Abstract: A system for improving the dynamic range of guidance systems for missiles d bombs by replacing pseudo-logarithmic amplifiers in the processing circuits with transimpedance amplifiers having feed back impedance operating in conjunction with lower bandwidth type logarithmic amplifiers in the log of the ratio circuits.

Abstract: A computer implemented control system which includes interface circuitry by which signal intelligence is taken in to the computer from external devices such as sensors and is fed out from the computer to external devices such as actuators which correctively adjust controlled parameters. An interface circuit for each of the several external devices is made "universal" in that either an analog input, bistate input, analog output, or bistate output device may be connected to any given one of the terminal points. A voltage follower amplifier sends the intelligence signal to an output device through a low-cost diode, with negative feedback taken from the downstream side of the diode. When an input device is elected for a given terminal point, simple program editing assures that the diode will be reverse biased to isolate the amplifier from the input signal path.

Abstract: A nonlinear noninverting amplifier design for receiving and amplifying an input signal in an optical communication scheme having a nonlinear inverting feedback is disclosed. The inverting feedback varies nonlinearly with the input signal to avoid saturation of the amplifier while providing a zero state input amplitude signal to reduce the amplitude of the input signal required to turn-on the feedback, thus allowing the amplifier to operate with a wide variation of optical generators, paths, and converters. A nonlinear noninverting amplifier design is provided which eliminates the need for automatic gain control circuitry and can be designed as an integrated circuit.

Abstract: An apparatus for separating dc current and ac current signal portions of a composite signal. The apparatus has a main current path for carrying the composite signal. This path splits into a dc current path and into two dc blocked ac current paths. At the node a virtual ground potential for the ac current signal portions is generated with the aid of an inverting amplifier with negative feedback located in one of the ac current paths. Thus, only the dc current portions flow over the dc current path. In a preferred embodiment, the dc blocking is implemented by a capacitor in each ac current path, and the inverting amplifier is an operational amplifier, whose non-inverting input is at ground potential, whose inverting input is connected with the respective capacitor and whose output is connected both with the inverting input via an ohmic negative feedback resistor and with an impedance in the other ac current path.

Abstract: A logarithmic amplifier which obtains accurate logarithmic output voltage and expands maximum current value and which realizes accurate logarithmic conversion by eliminating logarithmic conversion error voltage resulting from internal resistance of logarithmic conversion element using a voltage appearing when a forward current of logarithmic conversion element is applied to a resistor.

Abstract: A system for the high gain amplification of musical audio signals uses a control signal derived from the audio signal to automatically vary the current in the gain control circuit of the amplifier in response to audio signal level changes. A distortion circuit in the feedback path of the amplifier provides controlled distortion. The system may also provide for a variable control signal threshold level and for variation in control signal decay characteristics. The system may further provide a user variable maximum gain control.

Abstract: A soft clipping circuit particularly suited for use with audio signals avoids the need to use non-linear diode characteristics to determine the amount of clipping that is provided. A diode switching circuit which includes constant current sources is used to determine the output voltage of an amplifier at which clipping is to begin. Once this voltage is reached, the switching circuit disconnects the amplifier from a signal output terminal. At this time, the signal at the output terminal is determined solely by the values of resistors in a resistive dividing network connected between a signal input terminal and the output terminal.

Abstract: A fully differential non-linear amplifier includes an operational amplifier (12), a first input resistor (R1), a second input resistor (R2), a first feedback resistor (R3), a second feedback resistor (R4), a first clamping network (CN1), and a second clamping network (CN2). The first clamping network (CN1) is formed of a first P-channel clamping transistor (P10) and a first N-channel clamping transistor (N10). The second clamping network (CN2) is formed of a second P-channel clamping transistor (P12) and a second N-channel clamping transistor (N12). The gates of the first and second P-channel clamping transistors (P10, P12) are connected to receive a P-bias signal. The gates of the first and second N-channel clamping transistors (N10, N12) are connected to receive a N-bias signal. The non-linear amplifier clamps its differential output signal to a constant voltage level independent of variations in process and temperature.

Abstract: A switch circuit includes an input terminal, an output terminal, an amplifier having a non-inverting input node connected to the input terminal, an inverting input node and an output node, and a feedback circuit having a feedback path feeding a signal at the output node back to the inverting input node, a switch circuit being inserted in the feedback path and the output terminal being connected to the feedback path.

Abstract: An amplifier having at least a pair of gain levels for each of the AC and DC components of an input signal. The non-linearity in gain is achieved through the use of feedback which varies, in stepwise fashion, with input sigal magnitude.

Abstract: There is disclosed an amplifier device for use with a photodetector for amplifying wave energy signals received by the photodetector and converted into electrical signals. The amplifier device includes a first amplifier having its input connected to a junction between the photodetector and first and second photodetector load impedances. A negative feedback amplifier is connected to the output of the first amplifier. The negative feedback amplifier provides a feedback voltage to the first load impedance when in its first mode of operation and effectively reduces the voltage feedback to the first load impedance when in its second mode of operation. A switching device is provided to effectively switch the second load impedance in and out of circuit with the photodetector to effectively change the photodetector load impedance and alter the bias voltage to the feedback amplifier.

Abstract: An optical receiver comprises a plurality of sequentially-connected, symmetrically-constructed operational amplifiers having two complementary outputs. For the determination of the operating points and for suppressing the offset voltages, one output of each amplifier is connected by way of a negative feedback path to the second input of the first amplifier, whereas the useful signal is supplied to the first input of the first amplifier.

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: In an optical receiver for the reception of a modulated light beam, the beam falls on a PIN diode connected to the input of an amplifier which has a feedback resistor across it. This resistor is shunted by the series combination of a Schottky diode and of a PIN diode. The former diode ensures that a high magnitude pulse does not leave the receiver undesirably insensitive to a following smaller pulse. The latter diode, due to its low self-capacitance and low leakage, overcomes distortions due to the Schottky diode's higher self-capacitance and leakage. These effects are enhanced by providing the series-connected diodes with a low value (e.g. 0.2 volts) of reverse bias, due to the different connections of the diodes and the feedback resistor to a potential divider between the amplifier output and a point at a reference potential.

Abstract: A femtoammeter is disclosed which resists noise induced reversed bias of the ammeter amplifier and avoids long time constant recovery with unusually high measurement accuracy. The amplifier ammeter has a feedback loop which is provided with paired opposingly faced log diodes in parallel across the feedback circuit. Transients of negative or positive bias are accommodated without biasing the amplifier to a reverse polarity and having unacceptably long time constant recovery. Conventional temperature compensation, not possible with the parallel reversed diode configuration, is supplied by heat sinking the ammeter components, providing a log diode temperature sensor for the heat sinked components and controlling the heat sink operating temperature with a thermoelectric cooler. The temperature sensing log diodes output to a computer lookup table. The same temperature sensing log diode outputs to a bridge circuit operating the thermoelectric cooler.

Abstract: An output circuit amplifier has first and second stage amplifying transistors with an impedance circuit connected between the base of the first stage transistor and the collector-emitter circuit of the second stage transistor to draw current from the first stage transistor base, thereby keeping both transistors out of saturation. The impedance circuit establishes a voltage drop between the two transistors such that large output voltage swings are enabled at an output terminal connected to the second stage transistor. The collector-emitter circuit of the first stage transistor is connected directly to a positive voltage bus to avoid further saturation problems.

Abstract: An operational amplifier is disclosed having a phototransistor at its input for reading a bar code wherein the saturation point of an operational amplifier is controlled by a clamping feedback voltage having a positive control controlling the saturation point of the operational amplifier while prohibiting the operational amplifier from reaching its saturation point.

Abstract: This invention is directed to a narrow band filter for eliminating out-of-band noise in the oscillator signal of a doppler radar system. It provides a very high Q filter derived from a Bulk Acoustic Resonator's (BAR) high Q, L-Band response and uses thermal feedback to lock the BAR's response band onto the input frequency. The BAR is a very narrow band filter with a Q near 40,000 and a comblike frequency response having passbands occurring every 5 MHz, approximately. The comblike response of the BAR shifts down 60 KHz for every 1.degree. C. rise in temperature. In this invention a frequency sensitive heater is used to move the response comb of the BAR up or down in accordance with changes in the frequency of the incoming signal. The input frequency can be allowed to drift and the heat source will produce more heat or less heat, keeping the response right at the input frequency.

Abstract: An automatic gain control circuit is disclosed which enables the control of feedback gain to stabilize the circuit and increase its speed of operation. The AGC circuit includes an operational amplifier having a varactor diode coupled between one input and an output. The circuit is used to provide a feedback control signal in response to an output signal such that the varactor diode reduces loop gain when the output signal would otherwise cause an increase in gain and drive the feedback loop to instability, and increases loop gain when the output signal would otherwise cause a decrease in loop gain and lower response time.

Abstract: The distortion effects introduced in a complex multifrequency wave by parametric variations in individual active elements arising from signal and power supply variations in a circuit, such as an audio amplifier, are compensable through the use of replicas of the active elements, and the generation of a feedback signal incorporating comparable distortion. By high gain amplification of the feedback signal in a differential amplifier receiving an input signal that is not comparably distorted a comparison signal is derived containing distortion components. The comparison signal is used in a feedforward path which includes the circuit that is subjected to parametric variations in a sense to cancel the introduced distortions.

Abstract: An instrumentation amplifier having automatic offset error adjustment to null unwanted DC output signals. The DC gain of the instrumentation amplifier is first increased by reducing the internal negative feedback which increases the amplitude of unwanted DC signals; thereafter, an offset correction signal is provided to reduce the unwanted DC signals. The normal operating DC gain is restored and the unwanted DC output signal is further reduced.

Abstract: A variable electronic impedance circuit is constructed of a voltage-current converter whose input terminal is supplied with an input signal voltage, and a variable-gain current amplifier whose input terminal is supplied with an output current of the voltage-current converter and whose output signal current is fed back to the input terminal of the voltage-current converter.In order to prevent the undesirable oscillation phenomenon of the variable electronic impedance circuit immediately after the closure of a power supply, a control circuit which operates for a predetermined time after the closure of the power supply is especially arranged.Since an output signal from the control circuit inhibits the operation of the variable-gain current amplifier during the predetermined time, the unstable operation immediately after the closure of the power supply can be prevented.

Abstract: A level shifting circuit capable of operating with a wide range of impedances of a signal source without backflow of current and without a buffer circuit. A feedback element is coupled between an inverting input and an output of an operational amplifier. An output of a current source is connected to the inverting input of the operational amplifier while the signal to be level shifted is applied to the non-inverting input thereof. The current source may be a current mirror circuit and a temperature compensating diode may be coupled in series with the feedback element.

Abstract: An audio power amplifier includes an input amplifier stage and an output power amplifier stage. The output power amplifier stage comprises a p-channel field effect transistor and an n-channel field effect transistor having interconnected drain electrodes forming an output signal terminal. A driver circuit is provided for driving the p-channel and n-channel field effect transistors in a transconductance mode of operation in which the output current through the field effect transistors is directly proportional to the input voltage applied to the output amplifier stage. A first feedback path is provided between the output power amplifier stage and the input amplifier stage. A second feedback path is formed between the output and input of the input amplifier stage.

Abstract: In a noise reduction circuit comprising a combining circuit which generates a combined signal in response to signals supplied thereto, a main channel which supplies an information signal substantially unchanged to the combining circuit, and an auxiliary channel which receives the information signal and which supplies a modified information signal to the combining circuit for combining with the unchanged information signal, the auxiliary channel includes a high pass filter with a variable cut-off frequency which generates a filtered output signal in response to the information signal supplied thereto, a voltage-current converting circuit which converts the voltage level of the filtered output signal to a current and which supplies the current to the combining circuit, and an amplitude limiting circuit which limits the amplitude of the current supplied to the combining circuit.

Abstract: A pulse width modulated signal amplifier includes a power source, an integrator supplied with an input signal to be pulse-width-modulated and a carrier signal from a carrier signal oscillator, a comparator connected to the output of the integrator for producing a pulse width modulated signal, an output amplifier supplied with a DC voltage from the power source, and a negative feedback circuit connected between the input of the integrator and the output of the output amplifier. The negative feedback circuit becomes effective after a predetermined time from the time when the power source becomes ON so as to avoid the oscillation of the closed loop including the integrator.

Abstract: Feed-back paths of amplifiers, such as the alternately-operable AM and FM amplifiers of radio receivers, are interconnected by a first capacitor and earthed by a second capcitor, and each of the paths has a switching transistor for permitting current flow through only the feed-back path of the amplifier which is in operation. The AM amplifier has several stages including a final stage with transistors connected via respective feedback paths to two respective input connections. The FM amplifier is identical except that the component values differ.

Abstract: This dual operating mode switching power driving circuit arrangement comprises an amplifying circuit of conventional form which is operated substantially as a Class A feedback amplifier in a servosystem "following" mode and is switched to operate as a Class D amplifier in the "seeking" mode under program control calling for the latter mode and reswitched to the "following" mode only at the succeeding transition of the Class D waveform whereby transients are avoided. For operating in Class D mode, the Class A feedback loop is opened and the amplifier circuit is arranged so that the input wave now overdrives the input circuit and drives the output circuit between .+-. values of the energy potential, whereby the efficiency is very high.

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: In an active equalizer for selectively boosting or attenuating predetermined frequencies of audio or other electrical signals, and which comprises an inverting amplifier having an inverting input which receives the input signal through an input resistance and an output connected with the inverting input through a feedback resistance and at which the equalized output is derived, and an active filter for determining the frequencies to be boosted or attenuated; there is further provided a change-over switch having a boosting position in which the input signal is applied to the active filter, an attenuating position in which the output of the inverting filter is applied to the active filter and a neutral position, and a potentiometer connected between the output of the active filter and the inverting input of the inverting amplifier and being operable in concert with the change-over switch for determining the extent to which the frequencies determined by the active filter are boosted or attenuated.

Abstract: Disclosed is an apparatus having a signal attenuating portion for setting the gain or loss in amplitude of an electrical signal received by the apparatus, and alternatively, provides a gain of unity without a change of setting. The apparatus employs a plurality of switching devices which may be selectively opened and closed to provide the apparatus with a fixed gain of unity and alternatively predetermined losses or gains to the input signals.

Abstract: A highpass feedback loop for A.C. coupled amplifier circuits is disclosed, by means of which pulse undershoot recovery is accelerated. The feedback loop includes an operational amplifier which goes into limiting above a selected amplitude threshold so that for pulses exceeding the threshold the amplifier frequency response is unaffected.

Abstract: An automatic level control circuit for an operational amplifier 16 for minimizing spikes or instantaneous gain of the amplifier at a low period wherein no signal is received on the input. The apparatus includes a multi-branch circuit which is connected between an output terminal 26 and a feedback terminal 34. A pair of zener diodes 50 and 52 are connected back-to-back in series with a capacitor 54 provided in one of the branches. A pair of voltage dividing resistors 44 and 46 are connected in another of the branches and a second capacitor 42 is provided in the remaining branch of controlling the high frequency oscillations of the operational amplifier.

Abstract: A precision gain AC coupled operational amplifier circuit utilizing an integrated resistor voltage divider network and switched capacitors is provided. Precise gain is obtained by the use of integrated capacitors, and a low frequency stabilizing pole in the order of 10 Hertz is created by proper selection of the ratio of the resistors in the divider network.

Abstract: An impedance transducer is shown wherein two active elements of the same characteristics are formed on one thermally conductive base, one of these active elements is connected in a negative feedback circuit of a negative feedback amplifier, and the internal impedance of the other of these active elements is proportional to the input of the negative feedback amplifier.

Abstract: Apparatus for performing tests for determining the validity of a paper purported to be a valid instrument is presented. Fundamentally, the invention comprises a tray for receiving a paper offered as a valid instrument and maintaining the same in sliding relationship between a light source and reticle. A photocell is operatively connected to the reticle and senses light passing from the light source and through the paper and reticle. The output of the photocell is applied to an operational amplifier having a dynamic feedback network and the output of this amplifier is characteristic of both a grid pattern upon the paper and the optical density thereof. This output is then passed to an amplifier circuit which establishes an optical density domain and is operative to pass a signal only if the paper falls within such domain. This output is then passed to appropriate integrating and comparator circuitry to ultimately determine the validity of the paper.

Abstract: A feedback signal amplifier circuit having switchable closed loop gain in sponse to the output signal level of the amplifier for limiting the output signal level is presented. The feedback ratio of the circuit is switched by output signal level responsive diodes which derive signal level determining bias from both an unregulated power supply and the output terminal of the amplifier. A bias compensation network deriving bias from the unregulated power supply is connected to a bias sensitive input of the amplifier for tracking changes in power supply voltage which are reflected into the output of the amplifier for keeping the signal level determining bias of the diodes essentially constant and independent of changes of power supply voltage.

Abstract: A circuit for limiting transient intermodulation distortion in a amplifier system including an operational amplifier having a gain stage and a feedback network connected between the gain stage and the amplifier feedback port together with a pair of oppositely poled diodes, connected in parallel and coupled by means of capacitors between the amplifier output port and feedback port to limit the operational amplifier going to the supply rails under non-linear conditions thereby reducing the slew rate recovery time and therefore the amount of transient intermodulation distortion.

Abstract: Coil current loading the induction coils of an induction heating apparatus is directly sensed at the input from the tank circuit and the derived feedback current signal is used to control the power supply to the tank circuit be reference to a signal provided manually or automatically under process control. A voltage feedback signal is derived with a transformer from the input to the tank circuit for providing an input to a voltage limiter operative on the current controller when the voltage to the tank circuit exceeds an acceptable limit. A current limiter overrides the current controller to limit the load current by control of the current controller when the load becomes excessive.

Abstract: A transistor amplifier utilizing AC, for an orchestral instrument, having a non-inverting input, with a predetermined range of linear amplification, a feedback means including a first path independent of transistors for controlling the input within said predetermined range, a supplementary path parallel with said first path and including a zener diode having a breakthrough point at the upper limit of said range, and a plurality of auxiliary paths having breakthrough points higher than that of the supplemental path, and each including a resistor and a zener diode, and arranged with the resistors in parallel and the zener diodes in series, forming a cascade arrangement, and the auxiliary path together being in parallel with the first path.

Abstract: A negative-feedback circuit for use with a moving-coil loudspeaker and a host amplifier modifies the feedback signal from the output of the host amplifier in such a say that the velocity of the voice coil of the speaker more closely follows the signal voltage input to the host amplifier. The power output of the power amplifier is delivered to the voice coil through a low resistance, and a high resistance feedback path is provided from each side of this low resistance to the input of the host amplifier. Other reactive, resistive and non-linear elements may also be used with the high resistance feedback paths for improved operation.

Abstract: In a preferred embodiment of the invention the audio signal is bandwidth limited before being differentiated to provide either a positive or negative signal (depending on the slope of the audio signal) to a comparator which provides a corresponding logical one or zero at its output. A digital logic circuit connected to the comparator output is clocked to provide a digital output signal transition from a logical one to a zero or vice versa if its input has changed from a logical one to a zero or vice versa at least once during the clock period. The clocked digital output of the logic circuit is provided as an input to a computer where it is stored. The digital data is subsequently read out of the computer and provided to a filter and integrator to provide an audio signal replica of the filtered input audio signal.

Abstract: Input pulses are coupled through a delay network to a pulse amplifier. The amplifier includes feedback circuitry for correcting its output to a particular baseline level, generally zero volts. Within the amplifier feedback path is a gate, which is normally closed. Input pulses are also coupled to a pulse detector; whenever an input pulse is detected, the baseline gate in the amplifier feedback path is open, and the dynamic feedback operation is temporarily inhibited. During this time, the most recent previous level of baseline correction is retained.

Abstract: A technique for automatically varying the gain of a lock-in-amplifier with ogarithmically responding diodes placed in the feedback network so that the output is proportional to the logarithm of the input. Measurement of low or high level signals without manual changes of gain is then provided.

Abstract: A pre-amplifier for photomultiplier tubes includes means to compensate for the combined dark current and noise output of a photomultiplier tube without inducing a noise dependent offset voltage at the pre-amplifier output. A feedback amplifier and a compensating network, including a capacitor, cooperate to monitor the pre-amplifier output and during this time to maintain the feedback amplifier in a linearly responsive state while charging the capacitor to an amount necessary to clamp the average value of the most negative excursion of the pre-amplifier output to ground.

Abstract: An integrating capacitor is connected between the inverting input and the output of an operational amplifier. A plurality of resistors are connected in series to the inverting input. A plurality of capacitors are connected between the inverting input and junctions of the resistors respectively. The time required for the output voltage of the operational amplifier to reach a predetermined level is an exponential function of a voltage applied to the inverting input through the resistors.

Abstract: Disclosed is an amplifier for electrical signals obtained by means of a photoelectric transducer as a function of the intensity of illumination incident upon said transducer, comprising an operational amplifier adapted to be connected in series after the photoelectric transducer and having a feedback branch, wherein the feedback branch of the operational amplifier includes an electrical element having a nonlinear characteristic connected in parallel with a resistance.

Abstract: A gain and impedance switching circuit for an amplifier includes an AF amplifier having an input impedance connected between the input terminal thereof and a reference point and a feedback circuit connected between the feedback and output terminals of the amplifier, a first series circuit consisting of a first impedance and a first ON/OFF switch and connected between the input terminal of the AF amplifier and a reference point (such as ground) and a second series circuit consisting of a second impedance and a second ON/OFF switch connected between the feedback terminal of the AF amplifier and the reference point, the first and second ON/OFF switches being ganged with each other so as to change the input impedance and the gain of the AF amplifier simultaneously.

Abstract: A programmable amplifier includes an operational amplifier receiving an analog input signal of a given polarity and voltage range and a read only memory (ROM) control which actuates six switches in a resistor configuration connected to the amplifier in such a manner as to provide a selection of two gain factors and direct or inverted polarity output in response to combinations of digital signals on two input lines to the ROM.