| 摘要 |
PURPOSE:To decrease remarkably carrier leakage by providing a differential amplifier having a high common mode rejection ratio to an output section extracting a balanced modulation output so as to cancel an unnecessary common mode signal component appearing in the balanced modulation output. CONSTITUTION:The balanced modulator consists of transistors (TR) 2-12, resistors 14-20 and a constant current source 22. Color difference signals R-Y, B-Y are fed to bases 26, 28 of the TRs 10, 12. A carrier signal is fed to the bases of the TRs 2, 8 in a form of inversion. An output point formed between collectors of the TRs 2, 6 and the TRs 4, 8 is provided with the differential amplifier 30 halving a high common mode rejection ratio (CMRR), and the balanced modulation output is extracted from an output terminal 32. Through the constitution above, the carrier component of the TRs 2, 6 and the TRs 4, 8 is cancelled by the differential amplifier 30 and a signal decreased with the carrier component is extracted. |
