Gte Sylvania Incorporated

Gte Products Corporation

Gte Laboratories Incorporated

Rangaswamy Arumugham

George H Kam

Karol Siwko

William Frank Kruszewski

A compensated reference voltage source for providing a stable output voltage despite variations in operating voltage. The circuitry includes a series arrangement of a first resistance, a Zener diode, and a second resistance connected between a source of operating voltage and ground. A first transistor has its collector connected to the juncture of the first resistance and the Zener diode, its base connected to the juncture of the Zener diode and the second resistance, and its emitter connected to ground. A second transistor has its base and emitter connected directly to the corresponding electrodes of the first transistor and its collector connected to an output terminal. A third transistor has its collector connected to the source of operating voltage, its emitter connected to the output terminal, and its base connected to the collector of the first transistor. The base-emitter characteristics of the transistors are essentially identical. The voltage across the Zener diode remains constant despite variations in the operating voltage. However, the voltage at the collector of the first transistor varies because of changes in current flow across its base-emitter junction. Because of the interconnections, equal currents flow through each of the transistors. Since the base-emitter characteristics of the transistors are identical, the voltage drops across the base-emitter junctions of the first and third transistors are equal. Thus, the voltage at the output terminal is equal to the voltage across the Zener diode and remains constant despite variations in the operating voltage.

Compensated reference voltage source

A chrominance take-off circuit effecting a transmission zero at a predetermined frequency approximately equal to one-half the chrominance subcarrier frequency. The circuit includes a capacitive branch coupled in series with a parallel RLC branch that is resonant at approximately the subcarrier frequency. At frequencies below the subcarrier frequency the RLC branch is equivalent to a series-connected resistance and inductance. At the predetermined frequency the magnitude of the impedance of the capacitive branch is substantially equal to the magnitude of the impedance of the equivalent inductance, resulting in maximum attenuation of luminance signals at the predetermined frequency.

Chrominance take-off circuit

A high input impedance, low output impedance, temperature-stable tuning voltage interface circuit with substantial ripple rejection and negligible DC offset. The circuit comprises two transistors of opposite conductivity types, the first being coupled through a resistor to a supply voltage and through a temperature-stabilizing, DC-offsetting diode to the output of the second transistor. The rejection of the ripple voltage superimposed on the supply voltage is determined by the ratio of the value of the resistor to the effective resistance of the diode.

Tuning voltage interface circuit for electronic tuners

A network for combining a switchable and variable tuning voltage with an AFC voltage so as to effect a change in the tuning control voltage at a tuner's tuning control terminal is disclosed. The network compensates for time delays associated with the AFC time-constant in a manner such that the tuning control voltage responds in proportion to and substantially instantaneously with changes in the tuning voltage. The compensation reduces the probability of AFC false-locking phenomena when, for example, switching from one channel of a television receiver to another.

Network for applying a plurality of control voltages to a common control

Automatic frequency control (AFC) circuitry compensating for the nonlinear tuning voltage sensitivity characteristics of voltage-controlled tuners is shown. The circuit uses a nonlinear device, such as a zener diode, to develop an amount of error correction voltage that increases with increasing tuning voltage. In addition, through the use of a VHF Bandswitch voltage, the circuit controls an impedance in a network that combines the tuning voltage with the voltage developed by the AFC system in response to tuning errors. As a result, a greater amount of AFC error correction voltage is developed on Low Band VHF channels than on High Band channels. In this manner, substantially constant AFC pull-in range is maintained both within and among High and Low Band VHF and UHF channels.

AFC waveshaping circuit

Circuitry compensating for inherent nonlinearities in the tuning voltage sensitivity of varactor tuners, thereby providing relatively constant AFC pull-in range throughout the band of operating frequencies, is shown. In both the VHF and UHF bands, the AFC system develops an error correction voltage in proportion to the tuning voltage. With respect to reception of VHF channels, a gain switching circuit operates to reduce the proportion of AFC error correction voltage developed on a High Band VHF channel, thereby compensating for increased tuning voltage sensitivity on High Band VHF. With respect to reception of UHF channels, a tuning voltage sensing circuit operates to effect an error correction voltage that is a greater proportion of the tuning voltage when the tuning voltage is above a pre-determined value corresponding to approximately channel 60.

Adaptive wideband AFC system

A tuning voltage circuit for providing a tuning voltage which is corrected by an automatic frequency control error voltage for application to a voltage controlled radio frequency tuning means for a television receiver is shown. The voltage controlled radio frequency tuning means has a non-linear frequency versus tuning voltage characteristic which causes the sensitivity of the tuning means to the error voltage to vary over the frequency range of interest. The tuning voltage circuit includes a high impedance tuning voltage source which provides sensitivity compensation for the automatic frequency control error voltage to compensate for variations of the automatic frequency control pull-in range in the frequency range of interest.

Tuning voltage circuit

A signal combining circuit for combining a tuning bias voltage and an automatic frequency control error voltage for application to a voltage controlled radio frequency tuning means for a television receiver is shown. The voltage controlled radio frequency tuning means has a non-linear frequency versus voltage characteristic and the signal combining circuit includes a resistance means for coupling the error voltage to the tuning means input in a manner that compensates for the non-linearity of the frequency versus voltage characteristic of the tuning means to provide a substantially constant automatic frequency control pull-in range throughout the frequency range of interest.

AFC circuit

An automatic frequency control (AFC) circuit for a signal receiver having a tuner, intermediate frequency (IF) amplifier, video amplifier, and sync pulse separation means includes a discriminator coupled to the IF stage and a signal combining means coupled to the discriminator means and sync pulse separation means and to the tuner to effect a given 'pull-in' range for the tuner in response to error signals from the discriminator and an increased 'pull-in' range upon loss of sync signals from the sync pulse separation means when the tuner stage is increasingly detuned.

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Batavia, NY, United States of America

Rangaswamy Arumugham