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: A buffer amplifier circuit of a wideband tuner has an output transistor. The output terminal of this transistor is grounded through a matching transformer having two taps. One of the taps constitutes a terminal through which the output signal is delivered to a mixer circuit, while the other tap is grounded through a capacitor which constitutes, in cooperation with the matching transformer, a trap circuit. This trap circuit is adapted to trap a frequency which is about twice as high as the low region oscillation frequency of a local oscillator which produces an input to the buffer amplifier circuit.

Abstract: An analog integrated filter circuit includes a capacitance multiplier combined with a DC bias controlled current circuit designed to render the filter circuit insensitive to changes in the parameter values of the components caused by process variations or a temperature change therein. The capacitance multiplier circuit includes grounded or ungrounded capacitance multipliers in different combinations operatively coupled to the DC bias controlled current circuit so that the capacitance multiplier circuit can be used to construct a predictable low pass, bandpass or high pass filter circuit with frequency characteristics that do not vary over temperature.

Abstract: Monolithically integrable lowpass filter circuit having at least one capacitor and one ohmic resistor includes a signal input, a circuit node connected to the signal input, a first series resistor connected between the signal input and circuit node, an operational amplifier, a signal output connected to the output of the operational amplifier and to the circuit node, a second resistor connected between the circuit node and the signal output, a third resistor connected between the circuit node and the non-inverting input of the operational amplifier, and a capacitor connected between the non-inverting input and ground, the signal output being further connected to the inverting input of the operational amplifier.

Abstract: A non-inverting amplifier circuit having input and output terminals wherein the input impedance between the input terminal and a reference point is relatively low. The circuit comprises a first amplifier having a non-inverting input coupled to the input terminal, an inverting input, and an output coupled to the output terminal. A second amplifier is also provided, the second amplifier having a non-inverting input, an inverting input coupled to the output of the first amplifier and an output coupled to the non-inverting input of the first amplifier.

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.

Abstract: A tunable active high-pass filter particularly for use in hearing aids, which comprises merely a transistor as the active amplifying element. Three series-connected capacitors are connected between the input of the filter and the base of the transistor. A first resistor branches off from the junction between the first and second capacitors, a second resistor branches off from the junction between the second and third capacitors, and both resistors are connected, via a third resistor which is adjustable, to the emitter of the transistor which constitutes the output of the filter. A further resistor extends from the junction between the third capacitor and the transistor base to the source of operating potential which, for example, is positive. Preferably, each of the capacitors forms a high-pass filter with its respectively connected resistor with the first and second resistors, i.e.

Abstract: A vital narrow band-pass filter which operates in a fail-safe manner and includes a single stage input resonant circuit, an intermediate multistage parallel resonant circuit, and an output amplifying circuit for passing a given center carrier frequency signal and for attenuating adjacent carrier frequency signals.

Abstract: A high frequency power amplifier consists of a large number of serially connected transistors. The base connections of the transistors are connected to a potential divider consisting of reactive components, usually capacitors, which form part of a tuned circuit which is resonant at the frequencies at which the amplifier is to be used. The resonant currents flowing in the potential divider ensure that sufficient base current is available for the transistors to provide the required amplification.

Abstract: A filter circuit whose cut-off frequency is easily controlled and which can be manufactured as an integrated circuit. The base electrode of a first transistor is connected to an input terminal by a reactance element, such as a capacitor. Second and third transistors are connected in differential amplifier configuration, and a current source is connected to the common connection of the emitter electrodes thereof. The emitter electrode of the first transistor is connected to the base electrode of the second transistor and the base electrode of the first transistor is connected to the collector electrode of the second transistor. An output terminal is connected to at least one of the collector and emitter electrodes of the first transistor.

Abstract: A signal processing circuit for improving the signal-to-noise ratio of input signals, such as audio signals recorded on tape, has a low-pass filter circuit for controllably filtering signals at the lower end of the frequency spectrum, and a high-pass filter circuit for controllably filtering signals at the higher end of the frequency spectrum, with the high-pass filter circuit and the low-pass filter circuit defining the only paths through the signal processing circuit for the input signals. Associated control circuitry provides first and second control signals to control the attenuation of signals at the lower-frequency and higher-frequency parts of the spectrum, respectively, in dependence on the amplitude of the input signals in the respective parts of the spectrum.

Abstract: A selective amplifier whose gain characteristic is rendered approximately uniform over the entire frequency band to be amplified with no degradation in the S/N ratio. The amplifier consists of a band-pass filter and an amplifying element, in which a resistor for eliminating the ripples in the transmission characteristic of the filter is constituted with a feed back resistor for the amplifying element, the coil for the parallel resonance circuit in the filter is constituted as an auto-transformer and the capacitor in the serial resonance circuit of said filter is formed with the capacitance of a capacitive antenna respectively to thereby improve the S/N ratio. The amplifier is suitable to be used at the top of the high frequency stages in a radio receiver.

Abstract: A frequency characteristic-adjusting apparatus comprising a filter circuit formed of a first variable gain amplifier and a capacitor, a second variable gain amplifier for amplifying an output signal from the filter circuit, an amplifier for amplifying a signal denoting a difference between the amplitudes of an input signal to the filter circuit and an output signal therefrom, and an adder circuit for adding together output signals from the second variable gain amplifier and difference signal amplifier, and wherein the first and second gain amplifiers are connected to potentiometers, and the gains of the first and second variable gain amplifiers are varied in accordance with changes in the voltage supplied from the potentiometers to the amplifiers, while maintaining the prescribed relationship between the gains of the first and second variable gain amplifiers.

Abstract: A low pass active filter comprises multiple stages including multiple active devices, circuitry including resistance and capacitance AC coupling the stages in series sequence, and high impedance biasing resistance coupled between the first and last stage inputs, whereby the DC operating point is determined by one active device.

Abstract: A filter circuit, preferably a low-pass filter, whose cut-off frequency is easily controlled and which can be manufactured as an integrated circuit. First and second transistors are connected in differential amplifier configuration, and a current source is connected to the common connection of the emitter electrodes thereof. The base electrode of the first transistor is connected to an input terminal. A reactance element is connected between the collector electrode of the second transistor and a source of reference potential, such as ground. A third transistor has its emitter electrode connected to the base electrode of the second transistor and its base electrode connected to the collector electrode of the second transistor. An output terminal is connected to the emitter electrode of the third transistor.

Abstract: A low distortion phase compensated wideband amplifier system includes a low cost, power efficient Class C amplifier positioned along a primary signal path and a feedback loop coupled to provide negative feedback of distortion signal components in the amplified output signal. The negative feedback significantly reduces noise components including intermodulation noise while variable delay phase compensation permits a greater signal to noise ratio over a broader band of frequencies at the system output.

Abstract: An electronic filter comprised of three active filter sections (A, B, C) is provided to smooth the stepped signal from a digital-to-analog converter. The first section has a noninverting low-pass filter transfer function, and the second has an inverting transfer function designed to pass a narrow frequency band centered at the step frequency of the stepped output signal with sharp cutoff on either side of that narrow band. The third section adds the noninverted output of the first section to the inverted output of the second section. This third section has a lead-lag transfer function designed to reduce the phase angle between the signal at its output terminal and the stepped signal at the input of the first section.

Abstract: A transistor with a directly grounded base has an emitter connected through an impedance to ground and also connected through an impedance to a common negative terminal. A bias potential source is connected from the negative terminal through an impedance to ground and a collector potential source is connected from the negative terminal through an impedance to the collector. The floating potential sources allow high collector current without effecting the bias and, therefore, allow high power at relatively high frequencies and broad bandwidth.

Abstract: A surface acoustic wave filter arrangement is provided in which both filter and associated driving amplifier are arranged in the same integrated circuit package.

Abstract: A multiple-stage active RC distributed filter having multiple inputs and a single output for producing filtering of large groups of notes for tone coloration in electronic musical instruments. Output signals from the keying circuits may be applied to selected input stages of the filter through a resistor matrix to produce the desired tone coloration. Voicing may be further modified by one or more compensation networks at the filter output.

Abstract: An audio power amplifier is designed to have a wide band high fidelity response suitable for FM radio performance. The amplifier rolloff of gain versus frequency is made sufficiently steep to reduce the gain to a negligible level at the standard AM broadcast band. A stabilization network is incorporated into the amplifier to avoid instabilities that might result in oscillation. The amplifier has a very low AM broadcast band radiation so that it is useful in AM-FM radio receivers.

Abstract: A high frequency push-pull amplifier which includes an improved output circuit to eliminate spurious emissions, typically low frequency parametric oscillations. The output circuit includes a low pass filter with an inductive input so as to avoid a series resonance to any harmonic of the desired output signal of the amplifier. A resistive termination is provided to any of the in phase signal components between the push-pull amplifier and the low pass filter. Also, to inhibit any tendency towards parametric oscillations, the variation in output capacitance with respect to collector voltage of the transistors is minimized by placing a capacitor in parallel with the collector capacitance, which is several times the collector to emitter capacitance of the transistors at their normal collector voltage.

Abstract: A level shifting circuit for binary signals comprises a pair of equal value resistors connecting a common input signal to a pair of input terminals of a differential amplifier. A capacitor from one input terminal to ground stores the long term average input signal level for comparison with the instantaneous input signal level on the other input terminal. In another embodiment the range of input signal levels is modified by connecting equal value resistors from the input terminals to a voltage source. The invention provides amplification with minimum propagation delay, symmetrical propagation delay, a conventional logic level output signal and only requires a single power supply source for the amplifier circuit over a large range of input signal levels.

Abstract: An amplifier includes a network which generates additional output current for driving a substantially capacitive load as the frequency of an input signal is increased. The network comprises a plurality of rate discriminators which activate additional current sources at predetermined frequencies.

Abstract: A feedbeside correction circuit for correcting errors in the frequency response of a wideband amplifier includes a network which models the physical distortion-producing mechanisms of the amplifier semiconductor pn junctions. An input signal is applied simultaneously to the amplifier and to the feedbeside circuit. The feedbeside circuit produces a correction signal which is applied to a summing node and subtracted from the amplifier signal so that the amplifier output is substantially error free. The circuit may be used both for single-ended and differential inputs.

Abstract: A microwave signal amplifier comprising transistor having input and output terminals further includes input and output matching circuits connected to the input and output terminals, respectively, and corresponding bias supply circuits connected in parallel between said transistor and said input and output matching circuits, respectively. The input and output matching circuits are each implemented by high pass filters, and the bias supply circuits are each implemented by low pass filters. Furthermore, said high pass and low pass filters respectively have capacitors and inductors connected to the transistor, and said low pass filters have termination resistors.

Abstract: Current feedback is used to adjust the quiescent emitter current of an r-f amplifier transistor to prescribed idling or stand-by value, to avoid undesirable quiescent base-input-impedance conditions, but is disabled upon application of r-f drive to the base electrode of the r-f transistor so that operation which is other than Class A is not interfered with.

Abstract: An apparatus for driving a reactive load, comprises a plurality of N multnput elements N .gtoreq. 2, connected in parallel, capable of amplifying a band of frequencies. Two inputs of each element can be connected to sources of direct-current voltage. Each circuit element and elements connected to its inputs define a circuit stage. N means, each means connected to at least one of the inputs of the circuit elements, are capable of equalizing the gain of each of the N stages within a prescribed percentage. A transformer having N primary, input, windings and one secondary output, winding, is connectable to the load. Each of the N primary windings have their inputs connected to one of the inputs of the circuit elements. The transformer is so designed that its impedance, usually inductive, as seen from the load, balances the capacitive load, to be connected to it, over the bandpass of interest.

Abstract: A cable equalization resonant amplifier circuit for compensating for the signal-attenuation effects of a coaxial cable connected with the amplifier circuit and having a length of up to one-half mile. The gain of the amplifier circuit is matched with the attenuation characteristics of the coaxial cable over a wide range of frequencies by employing an LC resonant circuit with a Q of approximately 1 in the emitter circuit of an amplifying transistor. The gain for the amplifier circuit is established to match the attenuation characteristics of the coaxial cable at low frequencies by an RC circuit coupled with the amplifying transistor and the LC resonant circuit. The maximum or peak desired value of gain for the amplifier circuit at the resonant frequency of the LC resonant circuit is established by a resistor connected in series with the LC resonant circuit and a resistor in the collector circuit of the amplifying transistor.