Phase control circuit suitable for use in a tint control stage of a color television system

A controllable phase shifting circuit comprising:

• a source of first alternating signals;
• a source of second alternating signals in lagging phase relationship with said first signals;
• a first differential amplifier comprising first and second emitter coupled transistors each having an input terminal, a gain control terminal, and a collector output terminal;
• a second differential amplifier comprising third and fourth emitter coupled transistors each having an input terminal, an gain control terminal, and a collector output terminal, said collector output terminals of said third and fourth transistors being respectively connected to relatively antiphased collector output terminals of said second and first transistors;
• a first input signal network coupled from said source of second signals to at least one of said input terminals of said second amplifier;
• a second input signal network coupled from said source of second signals to at least one of said input terminals of said first amplifier for developing thereat a third alternating signal with a magnitude proportional to and a phase in in-phase relation with that of said second signals, and coupled from said source of first signals to said last-named input terminal;
• a third differential amplifier comprising fifth and sixth transistors with collector outputs respectively coupled to said gain control terminals of said first and second amplifiers for differentially controlling the signal gains of said first and second amplifiers;
• and
• a signal combining impedance network coupled at least to one pair of relatively antiphased collector output terminals of said first and second amplifiers for summing output signals from said first and second amplifiers to produce a resultant output signal with a phase with a phase within a range of phases between that of alternating signals respectively applied to input terminals of said first and second amplifiers, the phase of said resultant output signal being controlled in response to said third amplifier.

A controllable phase shifting circuit comprising:

• a source of first alternating signals;
• a source of second alternating signals in leading phase relationship with said first signals;
• a first differential amplifier comprising first and second emitter coupled transistors each having an input terminal, a gain control terminal, and a collector output terminal, said collector output terminals of said third and fourth transistors being respectively connected to relatively in-phase collector output terminals of said first and second transistors;
• a first input signal network coupled from said source of second signals to at least one of said input terminals of said second amplifier;
• a second input signal network coupled from said source of second signals to at least one of said input terminals of said first amplifier for developing thereat a third alternating signal with a magnitude proportional to and a phase in antiphase relation with that of said second signals, and coupled from said source of first signals to said last-named input terminal;
• a third differential amplifier comprising fifth and sixth transistors with collector outputs respectively coupled to said gain control terminals of said first and second amplifiers for differentially controlling the signal gains of said first and second amplifiers;
• and
• a signal combining impedance network coupled at last to one pair of relatively in-phase collector output terminals of said first and second amplifiers for summing output signals from said first and second amplifiers to produce a resultant output signal with a phase within a range of phases between that of alternating signals respectively applied to input terminals of said first and second amplifiers, the phase of said resultant output signal being controlled in response to said third amplifier.

In a color television receiver for receiving and processing a color television signal including a color information component and a color synchronizing burst component having a prescribed phase and frequency, said receiver including an oscillator providing a first oscillatory signal with a frequency substantially equal to the frequency of said burst component and in quadrature phase relation therewith and a second oscillatory signal in lagging quadrature phase relation with said first signal, phase control apparatus comprising:

• a first amplifier having a signal input coupled to said first signals, and a gain control input;
• a second amplifier having a signal input coupled to said second signals, and a gain control input;
• circuit means coupled from said source of second signals to said signal input of said first amplifier for developing a third alternating signal at said last-named input with a magnitude proportional to and a phase in predetermined relation with that of said second signals;
• gain control means having first and second gain control signal outputs respectively coupled to separate ones of said gain control inputs of said first and second amplifiers for controlling the signal gains thereof in complementary fashion;
• and
• a combining circuit for summing output signals from said first and second amplifiers to produce a resultant output signal with a phase within a range of phases between that of alternating signals applied to said signal input of said first amplifier and that of alternating signals applied to said signal input of said second amplifier, the phase of said resultant output signals being controlled in response to said gain control means.