Focus circuit

摘要

In a focus circuit for cathode-ray tube (40) of electromagnetic focusing type, a DC voltage (B4) which is made by dividing CRT anode voltage (B3) by a voltage dividing circuit (27) is compared with a reference voltage (B6) by an anode voltage variation component detection circuit (29), thereby to output therefrom a signal (Ve) of anode voltage variation component. This signal (Ve) and static focus adjusting DC voltage (B7) are summed and amplified by an output amplifier 30, which issues a current for correcting focus to electromagnetic focusing coil (31).