Variable impedance device for transistor automatic gain control

Claim 1

IN AN AUTOMATIC GAIN CONTROL CIRCUIT FOR A TRANSISTORIZED TELEVISION RECEIVER IN COMBINATION, AN INTERMEDIATE FREQUENCY AMPLIFIER STAGE HAVING A FIRST TRANSISTOR WITH BASE, EMITTER AND COLLECTOR ELECTRODES, SAID FIRST TRANSISTOR BEING ADAPTED TO HAVE INTERMEDIATE FREQUENCY SIGNALS APPLIED THERETO FOR AMPLIFICATION PURPOSES; A CONTROL TRANSISTOR HAVING BASE, EMITTER AND COLLECTOR ELECTRODES AND ADAPTED TO HAVE AUTOMATIC GAIN CONTROL SIGNALS APPLIED TO SAID BASE ELECTRODE THEREOF; CAPACITIVE COUPLING MEANS CONNECTED BETWEEN THE COLF; LECTOR-EMITTER CIRCUIT OF SAID CONTROL TRANSISTOR AND THE COLLECTOR-EMITTER CIRCUIT OF SAID FIRST TRANSISTOR FOR PROVIDING SUBSTANTIALLY ONLY ALTERNATING CURRENT COUPLING BETWEEN SAID CIRCUITS; DIRECT CURRENT BIASING MEANS COUPLED TO SAID COLLECTOR ELECTRODE OF SAID CONTROL TRANSISTOR; A SOURCE OF BIASING POTENTIAL COUPLED TO SAID TRANSISTORS AND MEANS FOR APPLYING AUTOMATIC GAIN CONTROL SIGNALS TO SAID BASE ELECTRODE OF SAID CONTROL TRANSISTOR TO VARY THE IMPEDANCE THEREOF AND THEREBY VARY SUBSTANTIALLY ONLY THE ALTERNATING CURRENT LOAD IMPEDANCE AND THE SIGNAL AMPLIFICATION FACTOR OF SAID FIRST TRANSISTOR SUBSTANTIALLY WITHOUT VARIATION IN THE DIRECT CURRENT BIAS APPLIED TO SAID FIRST TRANSISTOR WHEREBY SAID SIGNAL AMPLIFICATION FACTOR OF SAID FIRST TRANSISTOR IS VARIED SUBSTANTIALLY WITHOUT CHANGING THE CAPACITANCE AND THE TUNING OF SAID INTERMEDIATE FREQUENCY AMPLIFIER STAGE.