| 摘要 |
PURPOSE:To improve highly precise display of high horizontal deflection frequency and to make saw tooth current accurate by determining the polarity of a switching element and power source in the flow direction of reverse base current, and providing a reverse base current blocking circuit that prevent flow of reverse base current to an exciting transistor. CONSTITUTION:A signal P2 taken out from the collector of an driving transistor 2 is differentiated by a coupled resistor 22 and a coupled condenser 23 and supplied to an auxiliary driving transistor 21 as base current Ib. As time constant of a base bias resistor 24 and condenser 22 is selected to relatively small, the waveform of the base current Ib has large sag. The transistor 21 conducts for a fixed time tw4 from fall time t1 of the signal P2, and thereby, a square wave signal P4 is taken out from the collector. The signal P4 is supplied to an auxiliary driving transistor 26 through a coupled resistor 27 and make it conduct for a time tw4. Consequently, the reverse base current IB2 flows from the base of a transistor 4 to a negative power source -EB'. |
