JPS6411410A - Saw-tooth wave generating circuit - Google Patents

Abstract

PURPOSE:To stably generate a saw-tooth wave with a constant amplitude over a wide frequency range by varying the current value of a variable current power source according to the output of a comparator circuit and controlling the inclination of a saw-tooth wave outputted by an integration circuit. CONSTITUTION:A switching circuit 10 connects a constant current source 4 to the input terminal of the integration circuit 20 periodically in synchronism with a horizontal synchronizing signal f1 supplied to a signal input terminal 1 and then the circuit 20 generates the saw-tooth wave with a specific period synchronized with the signal f1. Further, the current value of a variable current generating circuit 60 is brought under feedback control according to the comparison output of a voltage comparator circuit 60 between the mean potential of the saw-tooth wave and a reference potential Vc to make the linearity of the inclination of the saw-tooth wave constant, and consequently the saw-tooth wave synchronized which has good follow-up characteristics and a horizontal synchronizing signal of frequency matching with various systems is generated by the circuit 20 and outputted from a signal output terminal 8. Namely, the saw-tooth wave with the constant amplitude over a wide frequency range is generated stably by the control over the circuit 30 by a 1st control circuit 50 and the control over the circuit 60 by a 2nd control circuit 80.