GB1379856A - Circuit arrangement for linear voltage-frequency or current-frequency conversion - Google Patents

Abstract

1379856 Pulse modulation circuits; sawtooth wave generators AKADEMIE DER WISSENSCHAFTEN DER DDR 22 Feb 1972 8126/72 Headings H4L and H3T In a linear voltage-to-frequency converter, Fig. 2, the input voltage S 2 charges a capacitor 2 rapidly via a switch 3 (which may be a semiconductor device) the capacitor being connected via an adjustable resistance R to the base of a transistor T1. The collector voltage S 1 is combined with the voltage S 2 and the resulting output S 3 is supplied to a comparator 5. When the voltage S 3 falls below the threshold value of comparator 5 the switch 3 is opened and the capacitor discharges non-linearly via resistance R. When the voltage S 3 exceeds the threshold value, the switch 3 is closed to cause recharging of the capacitor 2. In a modification, Fig. 3a, the capacitor 2 is charged by the input voltage S 2 via a diode D controlled by a transistor T1, a tunnel diode Tu with resistor R 2 acting as a comparator and the output pulses being taken from terminals 6, a pulse being emitted each time the voltage across the tunnel diode exceeds a predetermined value. In operation, if the current through transistor T1 falls below apredetermined level the working point of the tunnel diode reaches the peak of its characteristic and jumps to its high voltage state when the current continues to fall. This renders diode D conductive and capacitor 2 is charged rapidly, the working point of the tunnel diode characteristic moving towards its valley. The resulting rise in the base voltage of transistor T1 causes the tunnel diode to jump to its low voltage state, diode D is blocked, capacitor 2 slowly discharges via the base-emitter path of T1 and the cycle is repeated.