JPS5550733A - Saw tooth wave generation circuit - Google Patents

Abstract

PURPOSE:To make wider the dynamic range, to make equal the leading and trailing slope time, and to reduce the variation in the slope time variation due to temperature, by providing the switching circuit for the constant current circuit flowing the discharge current of capacitor. CONSTITUTION:The input signal (a) is fed from the input terminal, and the constant current circuit flowing the discharge current of the capacitor C2 (consisting of transistors TrT13-T15) is switched with the switching TrT16. Since the constitution like this is taken, the collector currents I5, I7 and I8 of TrT13-T15 are almost equal, and the charging current I6 (collector current of TrT12) of the capacitor C2 is equal to the collector current I5 of TrT11 with the constant current circuit constitution of TrT10-T12, the discharge current of the capacitor C2 I9 is nearly equal to I6. Accordingly, the saw tooth wave (b) in which the leading slope time T'3 by current I6 is equal to the trailing slope time T'4 by current I9, can be obtained. Further, since the low level of the saw tooth output is lowered to the level of VCFsat voltage (nearly equal to zero) of TrT14, T15, the dynamic range (difference between the low and high level of saw tooth wave) can be taken broader.