Simple triangle wave to sine wave circuit diagram

This circuit uses op amp uA741 to generate a sine wave with variable frequency. It is more difficult to generate a sine wave with variable frequency than a square wave with variable frequency. This circuit can convert positive and negative triangle waves into sine waves. The circuit is shown in the figure. Working principle: This circuit is actually an amplifier whose gain changes inversely proportional to the output voltage amplitude. Two 10k ohm potentiometers RP2 and RP3 set the slope of the output voltage near zero crossing. When the output voltage increases, RP3 should be adjusted until the diodes VD3~VD6 begin to be forward biased. In order to get the top of the smooth change of the sine wave, the potentiometer RP1 should be adjusted carefully, and the diodes VD1 and VD2 should be carefully selected. Use a dual-trace oscilloscope to observe the input and output, and carefully adjust RP1, RP2 and RP3, so that the circuit can be adjusted to the best state. The main disadvantage of this circuit is that it only works optimally when the input is 1.4V peak-to-peak.