Abstract: A power amplifier driven in the switching mode is started into oscillation by a pulse from an auxiliary oscillator when it is first activated. Reactive currents thereby resulting in an output filter network, containing a series resonant circuit followed by a parallel resonant circuit which is connected across a load impedance, then produce the switching in of a feedback circuit, after which the amplifier oscillates in a self-excited mode, at a frequency determined by the tuning of the resonant circuits.

Abstract: In an electronic tuning circuit for AM receiver including a radio-frequency tuning circuit and local oscillator circuit each using a variable capacitance diode, the local oscillator circuit comprises an oscillation coil; a padding capacitor connected in series with the oscillation coil; a first variable capacitance diode connected at one end in series with the oscillation coil; a first and a second fixed capacitor connected at one end in series with each other; and a second variable capacitance diode connected in parallel with the second fixed capacitor. The second fixed capacitor has its other end connected to a connection point between the padding capacitor and the first variable capacitance diode. The first fixed capacitor has its other end connected to the connection point between the oscillation coil and one end of the first variable capacitance diode. A tuning voltage is applied to the first and second variable capacitance diodes, thereby reducing tracking error over the entire receiving frequency band.

Abstract: A signal source for generating a well-controlled, predictable oscillating output signal within a short, predetermined and constant start-up time is disclosed. The invention includes a switchable current source for selectively providing an electrical signal to a tank circuit which, in response, provides an oscillating output signal. A control circuit, comprising a comparator is connected to the tank circuit for providing a control signal to the switchable current source which causes the current source to switch in response to the output signal. Particular embodiments of the invention include means for controlling the amplitude of the oscillating output signal, means for controlling the transconductance of the current source, and means for starting the signal source.

Abstract: An oscillator circuit which includes a differential amplifier in combination with a negative feedback network and a positive feedback network connected to the amplifier. One of these networks determines the frequency of the generated oscillation. In order to obtain an oscillation of constant amplitude, the negative feedback network comprises a current limiter active as a controllable one-port network which is connected between the negative feedback input of the differential amplifier and a fixed potential.

Abstract: A gyrator circuit usable in a resonant filter circuit comprises a first and a second transconductance amplifier circuit, A and B, respectively, having opposite conductances, which amplifiers are arranged in parallel between a first terminal a and a second terminal b and comprise a first capacitance C.sub.1 arranged between said first terminal a and an earth terminal m, which gyrator circuit simulates an inductance L.sub.g arranged between said second terminal b and said earth terminal m and comprises means for controlling the quality factor Q of said inductance, characterized in that the first transconductance amplifier circuit A comprises two series-connected inverting amplifier stages P.sub.1 and P.sub.2, in that the second transconductance amplifier circuit B comprises an inverting amplifier stage P.sub.3, and in that the means for controlling the quality factor Q comprise a first means P.sub.5 for influencing the output conductance q.sub.2 of the gyrator and a second means P.sub.

Abstract: An oscillator circuit having a coil and capacitor tank circuit, a clamp resistor connected at one end to the coil and a switch coupled to the clamp resistor and coil. The switch is operative to close in response to a first input logic clamp signal and shunt the coil with an impedance that causes the oscillation to stop quickly. In response to removal of the input logic clamp signal the tank circuit starts to oscillate from a known state. Preferably the clamp resistor has a value which equalizes the tank currents for the clamped and peak unclamped states.

Abstract: A circuit arrangement of a reading device for electromagnetic identification cards having inverters connected in parallel and an LC resonant circuit forming a transmitting oscillator which is influenced by the identification card to change the amplitude of an oscillating signal in order to recognize approach thereto of the card. Detection of the signal amplitude change is utilized to form pulses for subsequent data processing in which the influence of distance between the identification card and the reading device is minimized.

Abstract: A high-frequency heating generator comprising a multi-grid electron tube 15 for use in industrial systems in the range of several kilowatts to a number of megawatts. In order to obtain an economic high-frequency generator, the electron tube 15 comprises at least two grids 152, 153; of which a first grid 153 is connected to a positive feedback circuit (15') of the oscillator circuit. A source of bias voltage may be supplied to the second grid 152. A low voltage control circuit (16) is connected to either the first (153) or second (152) grid, and the anode 151 is connected to a non-controlled d.c. power source (13, 14).

Abstract: A high-frequency heating generator, comprising an electron tube (B) for industrial systems ranging from several kilowatts to a number of megawatts. In similar systems employing an electron tube oscillator a substantial amount of power is dissipated in at least one control element (T) connected in the electron tube cathode circuit at power leads below the maximum power level of the apparatus. To obviate this drawback, an impedance circuit (Z.sub.K) is connected in parallel with the control element (T), which circuit dissipates part of the power to be dissipated in the cathode circuit.

Abstract: A voltage controlled oscillator (VCO) has an LC tank circuit which is pumped by two out-of-phase feedback components. The combined effect of the two out-of-phase feedback components results in an effective feedback signal that is a function of the ratio of the magnitude of the two out-of-phase coponents. The magnitude of one of these feedback components is controlled by a CMOS subthreshold Gilbert multiplier. The frequency of oscillation of an oscillating signal within the LC tank circuit changes according to a control voltage applied to the Gilbert multiplier.

Abstract: A resonant circuit which includes the input capacitance of the clock pulse inputs of a shift register (10) is pulsed by a sinusoidal wave at voltage peaks of the wave by an oscillator delivering barely enough energy to overcome the damping of the resonant circuit. The oscillator may be crystal controlled and, instead of having a single ended output for delivering energy only on peaks of one polarity, may be in push-pull form reinforcing oscillation peaks of both polarities. This circuit is easily combined with arrangements for switching oscillator frequency from one value to another and/or arrangements for interrupting the clock pulse output for timed intervals after each loading or unloading of the shift register. The loss power dissipation is reduced to about 6% of the loss power dissipation of a square pulse drive for the clocking of the same shift register.

Abstract: Disclosed is a proximity switch which includes a current feedback time oscillator so that an object in proximity may be detected from the decline in the oscillation output. In order to increase the recovery speed of the oscillation which has dropped as a result of detecting an approaching object, in addition to a first comparison circuit for detecting the object from the oscillation output level, a second comparison circuit is provided for varying the feedback current to the oscillation circuit to the end of maintaining the oscillation level at a certain low level even when the object has come sufficiently close to the proximity switch to otherwise completely terminate the oscillation. By virtue of the increased response speed of the proximity switch, it may be used in an environment where a strong AC magnetic field is present.

Abstract: An oscillator disclosed has a resonant tank circuit inclusive of an inductor (L1), a capacitor (C1), a capacitor (C3) and a capacitor (C4) connected in series with one another. A signal amplifier (A) is connected in a feedback loop which includes capacitor (C3). An additional impedance (C5) is connected between the feedback output of the amplifier and the feedback signal dividing capacitors (C3) and (C4). This additional impedance (C5) improves tuning range, tuning linearity, phase noise performance, and provides a very flat power output at ultra high frequencies.

Abstract: An oscillator circuit operable in different modes. The oscillator circuit, when operated as a crystal oscillator, is initially operated as a standard inverter oscillator requiring a low start-up voltage. Once the circuit oscillates, an hysteresis feedback network is inserted in the amplifying section of the oscillator providing a clock signal with sharper leading and falling edges. The circuit thus enables the start up of the oscillator at low voltages and ensures greater noise immunity following start-up. The oscillator circuit, when operated as an RC oscillator, may be operated as a Schmitt-trigger oscillator as soon as the oscillator is turned-on.

Abstract: A circuit is provided which is capable of band switching a voltage controlled oscillator (VCO) while maintaining the relative sensitivity of the voltage controlled device and, hence, the control line voltage itself. The circuit includes an array of capacitors, including a pair of capacitors and a voltage variable capacitor (varactor), a switch, and a tuning coil. When the switch is in the open position, the pair of capacitors are connected in parallel with the varactor. When the switch is closed, the pair of capacitors are connected to ground, arraying themselves on opposite sides of the varactor. In this closed position, the overall capacitance of the tuned circuit increased, thus lowering the tuned frequency of the circuit. Since the switched capacitance (i.e., the capacitance which changes the tuned frequency of the circuit) is arrayed on both sides of the varactor, the varactor maintains its relative sensitivity.

Abstract: A low power, wide bandwidth oscillator capable of oscillating at frequencies of greater than 350 MHz and capable of being implemented in relatively few parts is disclosed. A switching section controls the resonant frequency of a resonator and is connected in DC series with an amplifier. A regulator-buffer section simultaneously serves as a voltage regulator and RF signal buffer.

Abstract: A variable frequency oscillating circuit of the general Colpitts kind in which the frequency of oscillation varies in accordance with the current in a constant current source and oscillation stability is high because the oscillator is of the general LC form. Resonance is provided by a solid-state resonator driving a transistor forming the Colpitts oscillator and which is connected to ground through a constant current source having a controllable current to set the frequency of oscillation. The response characteristic can be linearized using a compensating circuit employing additional constant current sources and current mirror circuits.

Abstract: A vital integrated circuit square-wave oscillator having an integrated circuit operational amplifier. A reference voltage dividing resistor network connected to an inverting input of the amplifier for providing a 50--50 duty cycle. An L-C tank circuit connected between the inverting input and a noninverting input for determining the frequency of oscillation. A starting capacitor for initiating the oscillating action and a regenerative feedback circuit for sustaining the oscillations.

Abstract: A new and improved method and apparatus is disclosed for detecting a target location with respect to an inductive tank circuit. A sensing field such as an electromagnetic field is established having an amplitude which changes in value due to the presence of a target in the sensing field. A first energy level is provided to maintain the field at an amplitude. A second energy level is provided to achieve a value for the field within the predetermined amount of time after initiation of the field.

Abstract: An LC-type oscillator employing a differential amplifier to switch a tank circuit in response to a feedback signal. A voltage controlled variable capacitor is employed to control the frequency of oscillation. The bias across the variable capacitor is closely controlled to avoid errors in the frequency of oscillation during the period of startup, which would otherwise create an undesired error in the oscillation frequency.

Abstract: A method of using the temperature coefficient of the copper resistance of an oscillating coil to compensate for the temperature coefficient of the quality factor of the same oscillating coil. To this end, a voltage proportional to the copper resistance of the oscillating coil is generated across the oscillating circuit. The oscillator according to the process comprises an oscillating coil which comprises a high frequency litz wire. In order to access the copper resistance of the coil one of the litz wires is separated from the other wire at a first terminal of the coil and separately connected to a second terminal of this coil. From this second terminal, the coil is seen as a bifilar coil. A constant alternating current source is connected to the second terminal in order to generates across the oscillating circuit a voltage proportional to the copper resistance of the coil. The oscillator is preferably used for proximity switches having relatively large switching distance.

Abstract: A low frequency sinusoidal oscillator, comprises a circuit which contains operational amplifiers, resistors and capacitors and has no inductor. The circuit, however, operates as an inductor. The circuit is arranged to resonate at a frequency which may be chosen by acting on only one component which preferably is a resistive component.

Abstract: In a television receiver horizontal deflection circuit, the deflection circuit oscillator includes an LC resonant tank network that is excited into sustained oscillation to develop an oscillator alternating output signal. A high voltage generator is responsive to the oscillator output signal and develops a picture tube ultor voltage at an ultor terminal. An ultor voltage representative signal is applied to the input of a disabling latch circuit of a television receiver high voltage protection circuit. First and second diodes are coupled across the inductive portion of the oscillator tank network, with the cathodes of the two diodes being coupled together at a junction in common with the output terminal of the disabling latch. If the ultor voltage exceeds a predetermined level, the latch is energized, forward biasing both diodes to provide a short-circuit across the tank network.

Abstract: A position sensing element forms a reactance (inductive or capacitive) in the L/C tuning circuit of an oscillator. The reactance varies as a function of the position of the sensing element relative to a predetermined object. This causes the resonant frequency of the oscillator to vary as a function of the position of the sensing element. The output of the oscillator is squared to provide a square wave signal, the frequency of which is a direct function of the position of the sensing element relative to the predetermined object.

Abstract: The resistance-inductance element used to determine the frequency of the frequency generator in the prior art circuits is replaced by an inductance-capacitance combination. As in the prior art circuits the frequency determining circuit is connected between the output and the inverting input of an operational amplifier to whose direct input a reference voltage is applied. However in the present circuit an inductance is connected from the output to the inverting input of the operational amplifier and a capacitance-resistance circuit is connected in parallel with the inductance. A capacitance connects the inverting input of the operational amplifier to ground potential. Resistors connected from the inverting input to the positive voltage supply and to the output terminal from the inverting input and from the direct input are used to change the slope of the curve of frequency vs. inductance.

Abstract: A logic system for charge-coupled device driver circuits includes a master oscillator for driving system logic circuits, which in turn generate signals for the non-bit-rate clock circuits. In addition, the system logic circuits generate a command which resets and synchronizes a separate resettable bit-rate oscillator to drive the bit-rate logic circuits which generate bit-rate clock waveforms. By maintaining separate oscillators for bit-rate and non-bit-rate functions, the logic system substantially reduces noise and therefore results in a clearer image from CCD area imaging array.

Abstract: The invention relates to electrical oscillators arranged to oscillate so as to produce a substantially sinusoidal output signal. The said oscillator includes a general impedance transvertor circuit arrangement having two differential amplifiers connected only to a plurality of resistive and capacitive impedance elements and arranged to simulate a tuned circuit with sufficient feedback to maintain oscillation within the tuned circuit. The transvertor circuit is an active device in the form of an impedance invertor circuit or a convertor circuit.

Abstract: The invention relates to electrical oscillators arranged to oscillate so as to produce a substantially sinusoidal output signal. The said oscillator includes a general impedance transvertor circuit arrangement having two differential amplifiers connected only to a plurality of resistive and capacitive impedance elements and arranged to simulate a tuned circuit with sufficient feedback to maintain oscillation within the tuned circuit. The transvertor circuit is an active device in the form of an impedance invertor circuit or a convertor circuit.