Improvements in or relating to a device for producing a periodic voltage of desired waveform shape

摘要

1,134,989. Function generators. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 7 Feb., 1967 [9 Feb., 1966], No. 5714/67. Heading G4G. A periodic function generator comprises (Fig. 1) two npn common emitter amplifying transistors T 1 T 2 whose emitters are connected to negative over a balancing current source S, the collectors are resistance connected to positive, and the bases are supplied with antiphased sawtooth voltage from source K. The emitters are also connected to an impedance network Z comprising parallel branches 1 to n each having a resistance R 1 to R n in series with a diode D 1 to D n connected to discrete points of a potential divider r 0 r 1 to r n energized from the emitter of a voltage source transistor T 3 whose base voltage is controlled by potentiometer P. The resistors of the impedance networks are graduated so that its conductivity varies proportionally to cos x where x = V/V 1 , V 1 is the maximum and V the instantaneous voltage of the sawtooth, and it is shown (Fig. 2, not shown) that the output voltage to load C interconnecting the collectors is proportional to sin x. In a modification (Fig. 3, not shown) difference amplifiers receive the emitter common point voltage and the sawtooth voltage and energize the transistor bases. The potentiometric control of the base voltage of transistor T 3 may alternatively be derived from the base voltage of transistors T 1 T 2 . Other periodic waveforms may be applied to the input and derived from the output.