Control circuit
AssigneeU.S. Philips Corporation
InventorAdriaan Cense
Life of this patent
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Abstract
In a control circuit having an emitter-coupled pair of transistors, to the base whereof a control voltage is supplied and whose emitter circuit is controlled by a signal source, the control voltage is also supplied to the emitter circuit to obtain a lower direct current through the transistor pair for a larger gain so that unwanted variations in the output d.c. voltage level are reduced.
Claims13
A control circuit comprising first and second transistors each having emitter, base and collector electrodes, input means coupling the emitters of the first and second transistors to a signal source, means coupling the bases of the first and second transistors to a control signal source for controlling the gain of the control circuit and further coupling the collector of one of said transistors to an output of the control circuit for obtaining an output signal thereat having an amplitude controllable by the control signal source, said control circuit further comprising a circuit included in the emitter circuit of the first and second transistors through which a direct current only flows and which is responsive to the control signal source for controlling a direct current component in the output signal in a sense opposite to that of the circuit gain.
A gain control circuit for an amplifier comprising, first the second transistors each having emitter, base and collector electrodes, input means for coupling the emitters of the first and second transistors to a source of input signal to be amplified, first means coupling the base electrodes of the first and second transistors to a source of gain control voltage for the amplifier, second means coupling the collector electrodes of the first and second transistors to a source of supply voltage and the collector of the first transistor to an output of the amplifier for deriving thereat an output signal determined by the gain control voltage, and third means coupling the emitters of the first and second transistors to a D.C. circuit through which a direct current only flows, said D.C. circuit including means responsive to the gain control voltage for controlling the direct current component in the collector of the first transistor in a sense opposite to that of the effect of the gain control voltage on said first transistor.
A gain control circuit comprising, first and second transistors each having emitter, base and collector electrodes, input means for coupling the emitters of the first and second transistors in common to a source of input signal, first means coupling the base electrodes of the first and second transistors to a source of gain control voltage, second means coupling the collector electrodes of the first and second transistors to a source of supply voltage and the collector of the first transistor to an output for deriving thereat an output signal determined by the gain control voltage, and third means coupling the emitters of the first and second transistors to the output of a circuit for controlling the flow of D.C. current in the collector of the first transistor, said D.C. current controlling circuit having an input coupled to said source of gain control voltage and means responsive thereto for controlling the direct current component in the collector of the first transistor in a sense opposite to that of the effect of the gain control voltage on said first transistor.
Dependencies are inferred from the claim text.