Abstract: A novel transformer is described for use in a static inverter in association with one or two switching semiconductor devices. The transformer produces an output for control of the associated switching device(s) which changes in sense from conduction aiding to conduction inhibiting as a function of the flux level in the transformer core. The invention is applicable to single loop cores, such as are assembled from two "U" cores. Control is effected by a primary and secondary control winding wound through an aperture pair, the aperture pair being oriented for "neutrality" of the second control winding to the main flux. The aperture pair creates a five branch magnetic path which permits optimizing the control voltage applied to the associated semiconductor devices both to enhance the switching efficiency when the switching device is initially turned on and to reduce stresses on the switching device by precluding transformer saturation when the switching device is turned off.

Abstract: The present invention deals with a pulse generator for generating short duration, high current pulses at a repetition rate which is substantially independent of variations in source potential, load or ambient temperature. The pulse generator employs a single transistor, relaxation oscillator configuration, in which the base electrode potential is maintained proportional to source potential and the emitter electrode potential is coupled in an RC network in which rate of change of voltage on the capacitor is proportional to the source potential. Regenerative feedback required for production of short duration, high current pulses is provided by a current transformer having a few primary and a few secondary turns wound on a magnetic core for close coupling. The output pulses, which are derived by a second current transformer, are suitable for turning on a switching transistor in a high frequency static inverter.

Abstract: A lighting network is described which includes a main gas discharge lamp, a standby lamp and a control circuit. The control circuit senses when the gas discharge lamp is operating normally and turns off the standby lamp. When the discharge lamp is not up to full light output after ignition or has gone out due to a momentary power interruption, the control circuit turns on the standby lamp. The control circuit includes a transistor amplitude discriminator and an electronic switch. The discriminator, which senses the voltage at the discharge lamp terminals, has a transfer characteristic which produces a "low" output over a "normal" range of terminal voltages and a "high" output for terminal voltages below and above the normal range. The electronic switch responds to "high" and "low" discriminator outputs to turn on or turn off the standby lamp, respectively.

Abstract: A smoke detector comprising a smoke detection cell of the ionization type and an electrical network which provides for ac operation of the detection cell. The impedance of the smoke detection cell is very high (40,000 megohms) and changes in the presence of airborne combustion products. The network senses the impedance change by a measurement of the current through the chamber assuming an ac source under a short circuit load condition, a technique facilitating the use of bipolar transistors.

Abstract: An alarm driver is described providing an audio frequency signal for operating the alarm of a smoke detector. The driver comprises a four transistor bridge in which the transistor input bias is momentarily interrupted at an audio rate to permit the bridge current supplied to the alarm to stop and change direction. Cross coupling is provided to achieve bistability in operation of the bridge, while commutation is achieved by utilizing energy stored in the inductance of the alarm to turn one pair of transistors on and the other pair off at each switching transition. The driver is designed for maximum reliability and minimum current drain and it is suited for battery operation. It is preferably fabricated by an integrated circuit process, typically using bipolar transistors and sharing the substrate with the other circuitry of the smoke detector.

Abstract: The present invention relates to an AM-FM receiver suitable for integrated circuit fabrication and having improved mode conversion means. The AM-FM receiver had a d.c. coupled IF broadband IF amplifier comprising a plurality of stages of emitter coupled transistor pairs. A d.c. feedback network is provided to balance the individual stages and to generate a control potential for further use in mode conversion. In the FM mode, the IF amplifier operates with a high, stable gain at the FM IF frequency with gain reduction for noise suppression purposes below the FM IF frequency. Frequency dependent noise suppression is provided by a capacitance associated with the degenerative network. In the AM mode, the IF amplifier operates at a controllable, medium gain with the degenerative effect on IF gain restored at the AM IF frequency by the addition of capacity to the degenerative network.

Abstract: An FM tuner having an improved automatic frequency control circuit and designed for use in an AM-FM receiver is described. The tuner employs a mixer transistor and an oscillator transistor connected in circuit so that they form a single series path across the bias source. This feature permits one to control conduction in both transistors by control of one and thus simplifies both biasing and mode conversion. Preferably, the transistor bias source and the source of AFC control potential are consolidated to save decoupling components. When the base of the mixer transistor is connected to the source through a low d.c. impedance, the AFC potential is transferred (less the mixer junction drop) to the collector of the oscillator transistor, where it provides sensitive automatic frequency control action. The circuit design uses a minimum of components.

Abstract: The present invention relates to semiconductor amplification means, which may be fabricated as a monolithic semiconductor structure, for use in an automatic gray scale control circuit for a color television receiver. During the blanking interval, the control circuit senses the cut-off voltage of each gun of a three gun color cathode ray tube and stores that voltage. During the video field, the stored voltage is used to energize the driver for the individual gun and to bias that gun. The AGS control function for each gun requires two amplifiers of high current gain, high inverse impedance, only one of which is on at a time, and a consolidation of the sensing and output functions in two terminals. These functions are achieved in a four transistor configuration in which two cascaded pairs of emitter follower transistor amplifiers are connected in a closed loop.

Abstract: An audio amplifier is described designed for integrated circuit fabrication and having controlled idling current. The amplifier includes a pre-amplifier designed to be driven from an AM or FM detector or a high impedance ceramic cartridge. The powder amplifier has a pair of like conductivity type output transistors connected in push-pull and driven by a novel interstage driver whose circuit configuration and component parameters are selected to reduce the idling current to a small predictable value. Measures are further provided, including two feedback paths, for insuring stability, minimizing distortion and hum. The amplifier is executed in an integrated circuit format with a minimum of outboarded components and a minimum "pad" requirement.

Abstract: The present invention relates to a novel automatic gray scale control circuit for a color television receiver. The circuit senses the cut-off voltage of each gun during the blanking interval, and uses a voltage equal to the cut-off voltage to energize the driver and bias the gun during the video field. The effect is to standardize the emission of each of the three guns against variation in gun cut-off voltage and to produce improved gray scale accuracy at the lowest emission levels. Since the gray scale adjustment is optimized at the lowest emission levels, where the eye is most intolerant to error in hue, one may avoid the need for manual adjustment of the cut-off point, and in cases where the gain does not vary widely from gun to gun, avoid the need for separate gain adjustment. Thus, the circuit may be used either to simplify or eliminate the color set up process at the factory when the receiver is manufactured. It may also reduce or avoid the need for readjustment after periods of use.

Abstract: A detector for AM or FM signals is described. The detector employs a differentially connected emitter follower pair to which an in-phase and a phase-shifted signal are respectively applied. The emitter follower pair produces an output waveform with controllably spaced zero crossings which is the "greater of" the applied waveforms. For FM operation, the phase shift is made linearly frequency dependent, being in quadrature at resonance. In FM operation, the zero crossings are sensed to produce a succession of variable width unidirectional pulses whose widths are proportional to the frequency deviation. Amplitude variations in the variable width pulses may then be removed and integration in a filter with an audio frequency time constant recovers the FM modulation information. For AM operation, a phase shift of 180.degree. is used, producing full wave rectification. The AM information is then recovered from the rectified signal using the same integrating filter used for FM.

Abstract: The present invention relates to an AM-FM receiver of the superheterodyne variety having a novel bias supply circuit wherein a common filter capacitor may be used for the bias supply, the AGC function in AM operation, and the AFC function in FM operation. The B+ bias is supplied through a controllable current source which adjusts the bias in accordance with the detector output. In the FM mode setting, automatic frequency control of the local oscillator is provided by bias adjustment. In the AM mode setting, automatic gain control of the IF amplifier and of the AM section of the tuner is provided by bias adjustment. The invention has preferred application to integrated circuit fabrication.

Abstract: An automatic gain control system applicable to a television receiver is described. Synchronizing pulses contained in the video detector output are sensed to obtain a measure of the signal strength. This is done by applying the detected output, containing the pulses, to a threshold circuit to produce current increments representative of the excess of said pulses over the threshold. The current increments thus obtained are then applied to a non-linear amplifier which, as a bi-directional source of current, supplies charging or discharging current, depending upon signal strength variation, to an integrating network to obtain a smoothed gain control voltage. The circuit is characterized by both fast attack and fast release and may be used with or without external gating. It is suitable for general AGC control in a television receiver which must be substantially immune to aircraft flutter.