Swept frequency sine/cosine wave generation circuit

 The circuit uses the MSFS5 selectable low-pass/bandpass switched capacitor filter to eliminate the harmonics of a square wave applied to its input. The clock of the MSFS5 is 100 times the input square wave. The 74HC390 and 74HC74 form a 25-divide and 2-divide circuit. The Q output of the 74HC74 is connected to the two 2-divide circuits of the 74HC390A, and the square wave frequency generated is 1/100 of the filter clock frequency, and the phase difference is 90°. The square wave of the CMOS level will saturate the filter, so the circuit uses a resistor divider composed of R1 to R4 to reduce the amplitude of the signal. The circuit in the figure can obtain a swept sine/cosine pair in the frequency range of 1 Hz to 25 kHz (click to enlarge).