GB1334823A - Burst signal gating circuit - Google Patents

Abstract

1334823 Burst signal gating circuits MATSUSHITA ELECTRONICS CORP 14 Feb 1972 [26 Feb 1971] 6832/72 Heading H4F A burst signal gating circuit suitable for being formed into an integrated circuit comprises two differential amplifiers including transistors 21, 22 and 23, 24. A transistor 25 supplies constant current to the emitters of transistors 23, 24 and transistor 20 supplies current, corresponding to a composite chrominance signal applied at 19, to the emitters of transistors 21, 22. The bases of transistors 22, 23 are connected to a constant bias voltage terminal 19 and the bases of transistors 21, 24 are supplied with gating pulses derived preferably from the flyback pulses. While a gating pulse is present transistors 21 and 24 are cut off and the burst signal appears at terminal 36. In the absence of a gating pulse transistors 22 and 23 are cut off and the chrominance signal appears at 37. The outputs at 36 and 37 may be interchanged by interchanging the functions of terminals 31 and 32. Preferably the constant current supplied by transistor 25 equals the D.C. current flowing in the emitters of 22, 22 to minimize the D.C. level difference between the burst and chrominance signal outputs.