| 摘要 |
PURPOSE:To prevent inoperative action of AVR circuit at switch on or an appearance of unsmooth picture, by making inactive the operation of the swiching circuit connected to the output of a differential amplifier and decreasing the set current by increasing fHO. CONSTITUTION:Between the common emitter of differential amplifiers Q16, Q17 constituting a voltage comparison circuit 4 and the current source consisting of Q12, Q18, R5-R7, a Zener diode Q22 is inserted, to saturate the transistor Q18 and to increase the horizontal oscillation frequency fHO when the power supply voltage is decreased. That is, by saturating Q18 when the power supply voltage is decreased, the collector current of Q18 is made smaller than the specified current value proportional to the power supply voltage and the switching operation of Q20 is made inactive, and a low bias VL is increased, UC=VH-VL is made smaller, and fHO is increased. |
