to the base of the other npn transistor t 4 of differential amplifier 11 as well as to the base of an npn transistor t 7 belonging to differential amplifier 13 the other npn transistors t 5 and t 8 of differential amplifiers 12 and 13 respectively have their bases connected to a node c which is connected via a resistor r o to ground and is also connected to a current source i b i t 1 2 k b where k b is a constant differential amplifier 11 is the main waveform shaper while the purpose of differential amplifiers 12 and 13 is to correct the transfer characteristic of differential amplifier 11 in such a manner that the resulting sinusoidal signal has no bends i e has a continuous first derivative in addition to transistors t 3 and t 4 differential amplifier 11 includes two diodes d 3 and d 4 which respectively connect the emitters of transistors t 3 and t 4 to a common current source i t k 1 where k 1 is a constant bulk lead and discrete emitter resistances of differential amplifiers 11 12 and 13 are schematically represented by resistors r the emitters of transistors t 5 and t 6 as well as of transistors t 7 and t 8 are connected to current sources i t k 2 where k 2 is a constant in the present embodiment all transistors are equal and the following relationships exist between the voltage differences across nodes a and b a and c and b and c and the output currents of the differential amplifiers 11 12 and 13 equ1 where u t is the so called thermal voltage proportional to the absolute temperature and z 1 z 2 and z 3 are.