Abstract: In a television receiver, a non-saturating kinescope driver amplifier arrangement includes an input current limiter circuit coupled between a source of video signal and a current responsive signal input of a feedback kinescope driver amplifier. The limiter circuit, e.g., including a diode limiter, limits the magnitude of input signal currents applied to the current input of the amplifier to prevent the amplifier from exhibiting a saturated conductive state.

Abstract: An input pulse having an amplitude to be sampled is coupled to a sampling amplifier via an input circuit including a capacitance. A switch couples a reference voltage to the capacitance during reference intervals preceding sampling intervals. The reference voltage is decoupled at the end of the reference interval, at which time an auxiliary reference pulse is self-generated at the amplifier input by passive circuit elements associated with the input circuit. The auxiliary pulse exhibits an amplitude and sense for negating the response of the amplifier to the input pulse when the input and reference pulses exhibit mutually equal amplitudes at the amplifier input.

Abstract: A color television receiver includes plural automatic kinescope bias (AKB) control systems respectively associated with plural electron guns of a kinescope which may exhibit mutually dissimilar electron gun conduction characteristics. Each AKB system includes circuit for deriving a signal representative of the electron gun black current magnitude, a source of auxiliary signal with a magnitude proportional to the bias of the associated electron gun during image blanking intervals, and a control network for providing a bias control signal to the associated electron gun to maintain a correct black current level. In order to maintain the correct black current levels of the electron guns in substantially the same mutual relationship as exhibited by the conduction characteristics of the electron guns, the control networks for each electron gun respond both to the magnitude of the associated derived signal and to the magnitude of the associated auxiliary signal.

Abstract: A system for automatically controlling the bias of a kinescope in a television receiver comprises an input sampling amplifier, and an input clamping network including a clamp capacitor. A reference voltage developed on the clamp capacitor is applied to the input of the sampling amplifier for establishing its initial reference bias condition. The amplifier conducts during sampling intervals for sampling signal amplitude changes referenced to the reference voltage provided via the clamp capacitor. The amplifier is rendered non-conductive at other times, to thereby effectively decouple the discharge path for the clamp capacitor, whereby the clamp capacitor is prevented from discharging significantly during intervals when the AKB signal processor is not engaged in signal clamping and sampling functions.

Abstract: An automatic kinescope bias (AKB) control system includes a sampling amplifier which provides an output current for charging and discharging a storage capacitor in response to the amplitude of a derived pulse representative of the black current level conducted by the kinescope of a television receiver. The derived pulse amplitude is greater than zero when the black current level is correct, and is applied to the amplifier via an input signal coupling path. During sampling intervals, an auxiliary pulse is applied to the input signal path with a magnitude and sense for negating the amplitude of the derived pulse at the amplifier input when the derived pulse amplitude corresponds to the correct black current level. Accordingly, the amplifier conduction and the voltage on the storage capacitor remain unchanged.

Abstract: In a television receiver including an automatic kinescope bias (AKB) control system, a kinescope cathode is driven by a video output amplifier. A feedback network is provided from the output to the input of the amplifier. A sensing resistor is included in the main current conduction path of the amplifier. During AKB operating intervals, a cathode output signal proportional to the cathode black current level is coupled via the feedback network for varying the amplifier conduction such that a voltage developed across the sensing resistor is proportional to the black current representative cathode output signal. This voltage is utilized to control the cathode bias to maintain a desired black current level.

Abstract: A DC coupled signal translating circuit for supplying auxiliary graphics information switching signals to a video signal processor. The switching signal comprises plural switching levels including a quiescent level. The translating circuit includes first and second complementary conductivity input transistors with interconnected emitter signal inputs for receiving switching currents representative of the graphics switching signals via a conductor which undesirably exhibits a parasitic capacitance. The transistors are biased to conduct a nominal quiescent current and develop collector output currents which are proportional to the input switching currents, and which are respectively coupled via current repeating networks to control inputs of the video processor. Switching delays attributable to the parasitic capacitances of the input coupling conductor are significantly reduced due to the emitter voltage clamping action of the input transistors for all conditions of the input switching signals.

Abstract: A television receiver includes means for generating a peaking component which is combined with a video signal to produce a peaked video signal, and a control circuit responsive to the peaked video signal during prescribed control intervals for automatically controlling a reference level of the video signal. The peaking component is attenuated during the control intervals to prevent the control network from responding to spurious signals including noise, which would otherwise be enhanced by the peaking generator and distort an output control voltage from the control circuit. In a system wherein the control circuit is arranged in a feedback loop with a peaking generator comprising a delay line, such attenuation also serves to stabilize the feedback control loop against oscillation.

Abstract: The DC output level of a video signal amplifier is compensated to remain constant as the amplifier is gain controlled in response to a gain control voltage supplied from a gain control circuit which also supplies a DC compensation voltage to the amplifier. The DC compensation is preserved by means of an additional network which senses the DC bias of both the amplifier and the gain control circuit, and corrects a deviation of the amplifier bias and the gain control circuit bias from a prescribed mutual relationship. The sensed DC bias of the gain control circuit is also used to establish a black reference level for the video signal.

Abstract: A signal sampling circuit comprising a signal inverting amplifier with a gain greater than unity, an input clamp network including a feedback switch, and an output sampling network including a charge storage device and a sampling switch is disclosed. The amplifier input to which signals to be sampled are applied is clamped to the amplifier output potential via the feedback switch during non-sampling, clamping intervals. During subsequent sampling intervals, the feedback switch is disabled and the sampling switch is enabled to couple the amplifier output to the storage device, so that the storage device develops a voltage sample of amplifier output signals referenced to the clamping potential.

Abstract: A signal sampling circuit comprising a switch network coupled to a transconductance amplifier for providing output currents proportional to input voltage, an input clamp network, and a charge storage device is disclosed. The amplifier signal input is clamped to a reference potential via a negative current feedback path when the switch occupies a first position during nonsampling, clamping intervals. During subsequent sampling intervals, the switch occupies a second position for decoupling the feedback path and coupling the amplifier output to the storage device, so that the storage device then develops a sample of amplifier output signals, referenced to the clamping potential, as a function of amplifier output currents.

Abstract: In a television receiver comprising a video output stage for supplying amplified image representative video signals to a color kinescope, a signal clipping network is included for inhibiting video signal amplitude transitions otherwise capable of inducing radio frequency interference (RFI) by causing the video output stages to change between saturated and nonsaturated conductive states. The network is disposed in a low level video signal processing channel of the receiver, and serves to clip peak transient signal amplitude excursions likely to induce RFI in the video output stage. The clipping network exhibits a "floating" clipping level to account for variations in the black reference level of the video signal, and therefore variations in the peak level of transients likely to induce RFI, due to unit-to-unit tolerance variations of preceding signal processing circuits.

Abstract: In a video signal processing system including a clamp for clamping the video signal to a reference level during periodic image blanking intervals of the video signal, and a kinescope for reproducing an image in response to the clamped video signal, apparatus for automatically limiting excessive beam currents drawn by the kinescope. A derived control signal representative of the magnitude of excessive beam currents is applied to the video signal processing path prior to the clamp. The control signal is inhibited during the blanking intervals, and serves to offset the D.C. level of the video signal in the black direction during image trace intervals to reduce the current conduction of the kinescope.

Abstract: A D.C. gain controlled differential amplifier exhibiting balanced operation and a linear gain control response. The amplifier includes input and output emitter coupled transistors and a current source transistor. Input signals are supplied to the base of the input transistor, and a negative feedback network is D.C. coupled from the collector to base of the output transistor. A D.C. gain control voltage varies the conduction of the current source transistor to thereby vary the gain of the emitter coupled transistors. The control voltage is also D.C. coupled to a collector signal output of the output transistor to maintain the output quiescent level substantially constant as the amplifier is gain controlled.

Abstract: In a video signal processing system including a kinescope for reproducing an image in response to an image representative video signal, a circuit for clamping a periodic blanking level of the video signal to establish a black level for a reproduced image. A clamping device clamps the video signal to a reference voltage during periodic blanking intervals of the video signal. The clamped video signal is applied to the kinescope through a direct current coupling network having a threshold conduction level. A locally generated blanking reference signal, of a magnitude substantially equal to the difference between the reference voltage and the threshold conduction level, is added to the video signal prior to clamping, so that the clamped video signal coupled to the kinescope exhibits a desired blanking level and unimpaired peak-to-peak amplitude.