Abstract: Disclosed is a a wide band frequency amplifier comprising the following: A first and a second transistor constitute a first push-pull amplifier circuit. A first current source is included, of which one end is connected to the second transistor base, the other end connected to ground. A first bias voltage source is interposed between the bases of the first and the second transistors. A third transistor is coupled with the first transistor in Darlington connection, thereby driving the first and the second transistors using an input signal. A fourth and a fifth transistor constitute a second push-pull amplifier circuit. A second current source is provided, of which one end is connected to the fourth transistor base, the other end connected to ground. A second bias voltage source is interposed between the bases of the fourth and the fifth transistors. A sixth transistor is coupled with the fourth transistor in Darlington connection, thereby driving the fourth and the fifth transistors using the input signal.

Abstract: A filter with adjustable edge steepness includes input terminals for applying a signal to be filtered. One of the input terminals is connected to a reference potential. A signal-forming device is connected to the input terminals for forming a first signal and a second signal from the signal to be filtered. The signal-forming device adjusts a difference between the first signal and the second signal. A subtraction device is connected to the signal-forming device for forming a differential signal from the first signal and the second signal. A frequency-dependent device has an input terminal connected to the subtraction device, an output terminal for supplying another signal, and a filter transfer characteristic to be delivered to the differential signal. An addition device has an output and is connected to the signal-forming device and to the output terminal of the frequency-dependent device for forming a summation signal at the output from the first signal and the other signal.

Abstract: An amplifying circuit of the invention comprises: a high frequency amplifying circuit for amplifying high frequency; a low frequency amplifying circuit for amplifying a low frequency; input filters which are provided on the input side of the respective amplifying circuits so as to pass the frequency components thereof; output filters having the same characteristics as those of the input filters; and an adding circuit for adding outputs of the output filters. Therefore, an output dynamic range of the whole amplifying circuit is equal to the sum of the dynamic ranges of the respective amplifying circuits, so that a large output which is not distorted even if a sound volume is raised is derived.

Abstract: The precision programmable attenuator of the present invention makes use of a pair of non-interactive parallel connected divider circuits to provide a flat frequency response over a wide bandwidth. A first of these divider circuits is a low frequency divider circuit which provides a predetermined attenuation of low frequency signals. The second high frequency divider attenuates the high frequency signals and does not interact with the low frequency attenuator. Therefore, each of these dividers can be separately tuned independent of the other. The implementation of the low frequency divider is a resistive divider network which provides a DC coupling of the input signal to the output. The high frequency divider is comprised of an adjustable capacitor divider network which is automatically electronically tuned to obtain the desired high frequency gain response.

Abstract: A system for extending the frequency range of an RF amplifier by improving the VSWR, and power handling capability of the amplifier, comprising a broadband reversing transformer, a first and a second amplifier coupled by means of a first and a second through-line quadrature coupler with the first quadrature coupler being connected to the inputs of the two amplifiers and the second quadrature coupler being connected to the outputs of the two amplifiers. The broadband reversing transformer is inserted in series with one of the two amplifiers enabling a signal at frequencies out of the passband of the quadrature couplers to pass through the through-lines port of the quadrature couplers, and thereby greatly extending the frequency range over which quadrature couplers may be used while, at the same time, retaining the usual combining and VSWR advantages of the couplers within their passbands.

Abstract: An audio power amplifier achieves a closed-loop bandwidth which is relatively independent of gain, and a very high slew rate capability, with a current feedback operational amplifier design. A separate operational amplifier which is connected as an integrator and operates at sub-audio frequencies compensates for the output terminal bias current of the first operational amplifier, thus mitigating the effects of current mirror mismatch in the current feedback circuit and allowing the overall output offset voltage to be significantly reduced.

Abstract: A high precision composite amplifier for use in a data acquisition subsystem of a Computerized Tomography (CT) scanner provides enhanced high speed response in terms of reduced settling time. The speed improvement is due to a novel compensation network in which a high frequency pole and a zero in the open loop response characteristic for the composite amplifier are forced to cancel despite component and temperature variations. The resulting amplifier exhibits a simple, higher speed, single pole response. An adjustable circuit is provided for adjusting the placement of the zero to assure optimum pole/zero cancellation.

Abstract: A dual path amplifier circuit configuration to obtain wideband and precision DC response includes a wideband voltage amplifier, an input termination, a virtual ground feedback amplifier, and a compensated attenuator. The circuit allows precision DC and wideband measurements through a common signal probe while maintaining the input impedance of the measurement instrument. An additional feature of the circuit is to selectively allow DC measurements before or after an attenuator. The circuit can provide combined wideband and DC signal output or separate wideband and DC outputs. Additionally, the circuit can use a DC offset to null the DC level of an input signal.

Abstract: Method and apparatus for amplification of an electrical signal whose frequency may range from zero to 300 MHz, and whose voltage level may range from 0.5 volt to 0.5 volt, with intermittent resetting of the zero voltage level provided for. One or two incoming signals are divided into low frequency and high frequency components, and amplification of each of these components is optimized by passage of the component through a separate amplification circuit. Input signals to the high and low frequency amplification circuits are intermittently chopped to allow resetting of the zero voltage levels of the amplifier.

Abstract: A DC-coupled multistage operational amplifier, the participation of the multiple stages of which, in defining the effective gain of the amplifier, is frequency dependent, such that high frequency signals are amplified by a single high speed stage and coupled directly to an output port. Low frequency signals, on the other hand, are coupled through both the high speed stage and a low frequency precision stage connected in cascade with the high speed stage. The gains of the respective high speed and low frequency precision amplifier stages are such that amplification of a high frequency input signal applied to an input port is effectively defined by the gain of the high speed first amplifier stage, so that an amplified high ferquency output signal derived from an output port is effectively derived directly from the output of the high speed amplifier stage.

Abstract: A limiter circuit divides the output of a low frequency amplifier into two parts which are respectively high pass filtered, and low frequency amplitude limited. The two parts may be recombined to form an audio output which is freed from clipping distortion at the low end, while the high end is increased. The invention is especially suited for environments such as automobiles, where the ambient noise level may be high.

Abstract: A wideband active quadrature 90 degree hybrid for increased bandwidths with low power losses and the capability to have gain. The 90 degree hybrid can be incorporated in small areas for MMIC (monolithic microwave integrated circuits) circuitry in the low microwave frequencies. The 90 degree hybrid comprises a plurality of 90 degree phase shift means, each preceded by an input amplifier. Each of the 90 degree differential phase shift means comprises a high pass and a low pass filter. The low pass filter outputs are added together and amplified. The high pass filter outputs are also added together and amplified. The resultant amplified signals are output with a phase differential of 90 degrees. The amplifiers supply gain which is lost in the 90 degree phase shifting.

Abstract: A variable equalization system is disclosed, in which a plurality of amplification cells having a plurality of filter groups with natural frequencies progressively increased four times are connected in series or in parallel, thereby making possible a variable equalization over a wide range of cable length.

Abstract: A monolithically integrable controller circuit, particularly for amplitude control in oscillator amplifiers, providing an actual-value detection by rectification, an input signal means-value suppression with a differential amplifier, and a set-point setting, includes a signal input of the controller circuit connected to the base contact of a first transistor. A low-pass filter is connected to the base contact of a second transistor and to the signal input. The collector contacts of the first and second transistors are connected to a potential. The emitter contact of the first transistor is connected to one of the inputs of the operational amplifier. A first capacitor is connected between the emitter contact of the first transistor and reference potential. A first constant current source is connected between the emitter contact of the first transistor and reference potential. The emitter contact of the second transistor is connected to the other of the inputs of the operational amplifier.

Abstract: Reduction of undesired r.f. harmonics, generated in the highest power power amplifier of a transmitter, is achieved by providing at least one alternate path for the undesired harmonics incorporating a relatively low powered power amplifier for at least one undesired harmonic component and causing the harmonic, in this alternate path, to have an amplitude that is substantially equal and a phase 180 degrees relative to the corresponding harmonic output from the main path and combining the outputs of the paths.

Abstract: Circuits for modifying the dynamic range of signals, particularly compressors and expanders for use in noise reduction compander systems, in which the advantages of fixed band characteristics (variable attenuation throughout all or part of the frequency band) and sliding band characteristics (variable attenuation through part of the frequency band achieved by a variable pass filter) are provided, without the disadvantages normally inherent in each characteristic. The outputs of fixed band and sliding band circuit elements variably selected by a combining means operated by a control circuit which senses signal frequencies and/or levels, the elements operating in generally the same level range and at least a partial overlapping in frequency range.

Abstract: A method of improving the frequency reproduction at frequencies higher than a certain break frequency (fs) of a bass amplifier known per se within the audio frequency range. The amplifier has a low-pass filter portion (ACE1) and a power amplifier portion (EF) with a current feedback portion (ACE2) in order to get a negative output impedance against the loudspeaker. According to the invention high-pass filtration is carried out from the break frequency (fs) and upwards to about 20 kHz of the signal coming to the amplifier and thereafter a phase shift (.rho.) is carried out so that a cophasal state is obtained at the break frequency (fs) before the power amplifier portion (EF).

Abstract: In a selectable tuner preamplifier with a field-effect transistor tetrode comprised of a compound semiconductor and having the high-frequency input signal fed to one gate electrode and the control signal for controlling the high-frequency input signal fed to the other gate electrode, a component with a diode characteristic is provided for prevention of undesired current flow at the gate electrode controlling the high-frequency input signal when a band is selected and control voltage is applied.

Abstract: A system which corrects for adverse characteristics such as reactance, inertia and resonances of a power amplifier driven load such as a speaker or multiple speaker system. Program voltage is applied to a reference load which has electrical characteristics which simulate characteristics of the driven load, and the response of the reference load to the program is used to develop a correction voltage signal for the driven load. The program and the correction voltage signal are simultaneously applied to the power amplifier to simultaneously reproduce the program and correct for the adverse characteristics of the load.

Abstract: A plurality of common emitter transistor amplifiers have the output of a single operational amplifier applying an AGC signal to their bases. An input of the operational amplifier is connected to the collectors through respective diodes to isolate and to selectively form a feedback loop for the on amplifier from the off amplifier. Another input of the operational amplifier receives the AGC voltage so that the operational amplifier varies the base current and hence the gain of the common emitter transistor which is on.

Abstract: Second and third-order RC active filter sections are described both based on a similar basic twin-tee network. The circuits include a single operational amplifier and are such that the poles and zeros of the network can be adjusted with little interaction by varying resistances in sequence. It is possible to construct the sections using capacitors of wide tolerance.

Abstract: An adaptive signal weighting system is disclosed for use in transmitting an electrical information signal of a predetermined bandwidth along a signal path. The system can be used to encode or decode the signal. The system comprises filter means disposed in the signal path for varying the gain impressed on the portion of the information signal within a first select spectral region within the preselected bandwidth. The gain is varied in response to and as a function of a first control signal. Means are provided means for generating the first control signal in response to and in accordance with the signal energy of the information signal substantially within at least a part of the first select spectral region.

Abstract: A band-pass filter includes an arrangement of individual filter sections and means for weighting and summing the band-pass functions of the filter sections such that the active conjugate pole pairs are arranged in the z plane on a circle concentric to the unit circle and spaced by equal angles with the exception of corrector poles, which are spaced by half-angle increments from the adjacent poles. In the embodiment of the invention described, the filter sections are in the form of digitally controlled switched capacitor filters.

Abstract: A trigger circuit for use in an oscilloscope comprises a DC amplifier for low frequency amplification and high-frequency amplifier arranged to provide wideband trigger signal amplification while providing typical trigger coupling modes, such as AC, DC, high-frequency reject, and low-frequency reject.

Abstract: A compensation method and apparatus for a roughly compensated RC attenuator using fixed resistors and fixed capacitors. Any difference of the high frequency attenuation ratio from the low frequency of DC attenuation ratio is detected and corrected by using multiplier for increasing or decreasing high frequency components at the output from such RC attenuator, thereby allowing digital or remote compensation of RC attenuator without using variable capacitors.

Abstract: Improvements in compressors, expanders and noise reduction systems are disclosed which reduce the susceptibility of such circuit arrangements to undue control by signals outside the pass-band(s) (i.e., stop-band signals) in which the circuits are active. Level dependent circuitry operates, particularly by means of non-linear processing, to reduce the circuit response to the effect of stop-band signal components at high input signal levels.

Abstract: Comb filter having a comb like band pass characteristic curve by using an ultrasonic delay line (9) is improved to reduce its size. An input signal is given through an impedance element 13 to a single terminal 10a of an improved delay line 9, wherein the single terminal serves as the input terminal and at the same time as the output terminal. Signals at both ends of the impedance element 13 are given to a mixing circuit 15 for summing or subtracting thereby. In the improved delay line 9, the ultrasonic wave radiated from the input terminal travels twice the conventional delay line and comes back to the original terminal, and thereby a sufficient propagation distance is obtainable in a small delay line.

Abstract: A system which corrects for adverse characteristics such as reactance, inertia and resonances of a power amplifier driven load such as a speaker or multiple speaker system. Program voltage is applied to a reference load which has electrical characteristics that simulate characteristics of the driven load, and the response of the reference load to the program is used to develop a correction voltage signal for the driven load. The program and the correction voltage signal are simultaneously applied to the power amplifier to simultaneously reproduce the program and correct for the adverse characteristics of the load.

Abstract: A circuit for noise reduction is disclosed, including a first signal path connected to receive an input signal and including a high pass filter for providing substantial de-emphasis of the lower frequency components of the input signal relative to the higher frequency components thereof and a variable gain amplifier for amplifying the output of the high pass filter with controllable gain. A second signal path is connected to receive the input signal and provides little or no de-emphasis of the higher frequency components relative to the lower frequency components of the input signal. The outputs of the first and second signal paths are summed to produce a noise-reduced output signal. The gain of the variable gain amplifier is controlled so as to exhibit higher gain when the input signal level is relatively low and to exhibit lower gain when the input signal level is relatively high.

Abstract: A signal conditioning system is disclosed for modifying the dynamic range of an electrical input signal. The system comprises gain control means for controlling the gain of the input signal as a function of a gain control signal, and control signal generating means for generating the gain control signal. In accordance with one aspect of the present invention the control signal generating means comprises (1) means for generating a first signal as a function of the amplitude of the input signal, and (2) means responsive to the first signal for generating the gain control signal as a function of only those portions of one polarity of the time derivative of the first signal. In accordance with another aspect of the present invention means are provided for substantially lengthening and/or linearizing the release behavior of the control signal waveform applied as the control signal input signal to the gain control means.

Abstract: A circuit providing a known change in a parameter of a function without interfering with the basic operation of the function is utilized in an audio circuit "loudness contour" control. Bass and treble controls function independently of the volume setting while desired contours are obtained at each volume control setting.

Abstract: Frequency characteristic adjusting apparatus used in sound apparatus or the like, in which an input signal is divided into first and second frequency bands after being amplified, the gain of the signal of the first frequency band controlled by first and second gain control circuits respectively, the gain of the signal of the second frequency band controlled by third and fourth gain control circuits respectively, and the output signals from the first and second gain control circuits added and negatively fed back to the amplifier. The output signals from the third and fourth gain control circuits are also added.

Abstract: An amplifier circuit arrangement comprises an inverting (2) and a non-inverting amplifier (4) connected between a common input (1) and respective inputs of a summing circuit (6). The gains of the amplifiers are unequal for low amplitude input signals but are arranged to produce substantially equal antiphase limited outputs for high amplitude input signals. By making the gains of the amplifiers greater than the difference between their gains, a rapid transition is obtained from a situation where the gain of the arrangement corresponds to the numerical difference between the amplifier gains, to one where it has fallen to a low level. This property can be used in a phase-locked loop of which four examples are given, when the beat frequency output of a phase sensitive detector connected to the input of the amplifier arrangement is large, the output of the summing circuit (6) will be low.

Abstract: A signal processor for use in association with a frequency analyzer, can operate in the frequency translation mode or the filter mode.The signal processor comprises a first low pass filter, the signal from which is fed to two first parallel programmable gain amplifiers controlled by a first digital function controller. The signals then pass via two, second low pass filters to two second programmable gain amplifiers controlled by a second digital function controller. The signals from the second amplifiers are then added by an adder and filtered by a third low pass filter.The first controller is controlled by a frequency signal equal to the frequency in the middle of the bandwidth being translated and the first filter is controlled by a frequency which is a multiple of the control frequency to the first controller.

Abstract: A tone control circuit is provided having several parallel channels each of which comprises an electronic potentiometer. In each of the channels is disposed a filtering element. Thus, for an output terminal common to the different channels, each of the channels comprises a filter comprising a series element corresponding to the series element of this channel and a parallel element corresponding to the series elements placed in parallel of the other channels. The present invention simplifies the construction of tone control circuits in the form of integrated circuits.

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: The present invention provides a modified distributed amplifier which is capable of accepting two or more independent inputs and amplifying them without giving rise to a large number of significant intermodulation products. This modified distributed amplifier effectively comprises two or more unmodified distributed amplifiers (as V.sub.11 to V.sub.18 and V.sub.21 to V.sub.28) joined so as to have a common output line (10) but individual, independent, input lines (111 and 211). The join is preferably "back-to-back" (in a parallel sense) so that the individual distributed amplifiers are in some sort of interleaved arrangement.

Abstract: A signal to be delayed is applied to a frequency selective path including an inverting active bandpass filter and to a non-frequency selective path including a voltage-to-current converter. The paths are coupled to a signal combiner which produces an output current having a first component proportional to the output current of the converter and a second component directly proportional to the filter output voltage and inversely proportional to the value of a gain control resistor. The resistor is selected to provide a predetermined ratio of the output current components to provide an overall allpass characteristic for the delay circuit and biased to conduct no current under quiescent signal conditions thereby reducing power dissipation. Several circuits may be cascaded for such purposes as peaking and delay equalization in television receivers, video disc players or the like.

Abstract: A multiple band frequency response controller for use in audio applications, to precisely control and equalize audio system response. The frequency response controller shown will adjust response in ten octave bands. The unique feedback system used will generate response curves of increased smoothness and accuracy. In addition, the method shown will be readily adaptable to external control by analog or digital control signals.

Abstract: A bandpass filter circuit includes first and second resistors connected in series between input and output terminals thereof, an amplifier having a gain of three and its output connected to the output terminal, and an RC circuit network connected between the connection point of the first and second resistors and the input of the amplifier and having bandpass characteristics. The RC circuit network comprises a series combination of a third resistor and a first capacitor connected between the connection point of the first and second resistors and the input of the amplifier, and a parallel combination of a fourth resistor and a second capacitor connected between the input of the amplifier and a common terminal of the filter circuit. The third and fourth resistors have an equal resistance value and the first and second capacitors have an equal capacitance value.

Abstract: An audio power amplifier with class-D push pull output stage is disclosed using a "mixture" of pulse-width modulation and pulse-amplitude modulation and driving the class-D push pull output stage with the resulting combination signal. To do this, the digital output signal of the analog-to-digital converter in the input stage is split up in such a way that only its high-order bits control the pulse-width modulator, while the other low-order bitsare changed into the aforementioned pulse-amplitude-modulated signal by means of an analog-to-digital converter.

Abstract: A multiple-feedback path bandpass/bandreject filter which exhibits a nearly constant Q over a predetermined frequency range, and which is tunable by means of a single variable impedance element is provided. A Thevenin equivalent voltage source is placed in series with the tuning element, wherein the Thevenin voltage is a predetermined constant fractional amplitude of the bandreject output voltage, or its equivalent.

Abstract: An improved system for compressing or expanding the dynamic range of an electrical input signal of the type which includes a variable gain device for controlling the gain of the input signal and a circuit for generating a control signal for the variable gain device including a rectifier for producing responsively to the input signal a DC signal which substantially follows dynamic variations of the input signal. The improvement resides in the provision in the control signal generating circuit of a network of at least three signal paths having a common input terminal connected to receive the DC signal and a common output terminal connected to the variable gain device for coupling a control signal thereto, which signal paths have differing time constants and are automatically selectable as a function of the rate and amount of change in amplitude of the DC signal.

Abstract: A unidirectional current with i-f variations superimposed thereon is applied to the interconnected emitters of a pair of transistors, the collectors of which are coupled to a succeeding stage by a narrow-band filter and by a wide-band filter respectively. The unidirectional current with i-f variations is amplified by a selected one of the transistors and filtered accordingly, depending upon which of two polarities of potential is applied between the bases of the transistors.

Abstract: An audio processing system for maximizing the efficiency of transferring audio frequency signals. Signals to be processed are supplied to a bandpass input filter, then to a primary active frequency control. Its output drives a primary voltage compressor selectively limiting audio dynamics to a predetermined window, the latter being controllably preset and driven with different audio bands of amplitude determined by the primary frequency control to maximum compression levels indicated by a visual indicator. The output of the primary compressor is presented to a secondary active frequency control driving a secondary dynamic compressor with different audio bands. A second visual indicator indicates maximum compression levels of the latter. An automatic gain control (AGC) tied to the secondary compressor supplies feedback to the primary voltage compressor via AGC circuitry to control primary compression as a function of average, overall dynamic compression of the system.

Abstract: An amplifying device comprising a pre-amplifier, a first high power amplifier of a relatively bad lineality for amplifying the outputs of the pre-amplifier, a first impedance element for applying the outputs of the first amplifier to a load, a negative feedback circuit for feeding back the outputs of the first amplifier to the input of the pre-amplifier and a second low power amplifier of the relatively good linearity for amplifying the inputs of the first amplifier and supplying the outputs through a second impedance element to the load. The amplifying device can cancel the distortion in the high frequency band caused in the first amplifier through the first and second impedance elements by the outputs of the first amplifier.

Abstract: In a two-band compander pre-emphasis is carried out during compression and de-emphasis during expansion in the lower frequency range. Noise suppression is improved by this measure.

Abstract: A multi-channel audio power amplifier is arranged to amplify, by an analog amplifying circuit, high frequency range components of an audio signal and to amplify low frequency range components of said signal by a class D amplifying circuit, to thereby enhance the power efficiency of the amplifier. The carrier frequency of the class D amplifying circuit is set lower than that employed conventionally, to eliminate spurious radiation of the carrier signal.

Abstract: In a frequency characteristic adjusting circuit having an arrangement of at least one adder, a filter circuit and feedback and/or feed forward means the transfer factors of which and the peak or dip of the filter circuit are freely selectable. Adjustment of the center frequency and Q are independent.

Abstract: A tone control circuit includes a variable gain amplifier circuit, a first mixer combining the variable gain amplifier output with a tone control circuit input and providing its output signal to the variable gain amplifier input, and a second mixer combining the outputs of the first mixer and variable gain amplifier. The mixers may be either adders or subtractors as long as the natural logarithm of the overall gain of the tone control circuit varies substantially linearly with changes in the feedback ratio of the variable gain amplifier.