Make a signal source with MAX038

A signal source was made using MAX038 (see Figure 1 for the pin diagram) to observe the output waveform of the homemade 1-10kHz bandpass filter. The circuit is shown in Figure 2. MAX038 is a high-precision function generator with an output frequency range of 0.1Hz to 20MHz; output impedance: 0.1Ω; when the voltage of pin 7 (DADJ) is adjusted between +2.3V and -2.3V, the duty cycle of the output waveform varies between 15% and 85%. In Figure 2, DADJ = 0V, and the duty cycle is 50%.

Pin ⑧ (Ao) and pin ④ (AJ) of MAX038 are output waveform selection (see attached table). The waveform selection can be realized by using the circuit shown in Figure 3. CD4520 is a synchronous counter. Press the s key to count up. When the count reaches 3 (i.e. Q0Q1 is 11), the counter is cleared to o. Q0Q1 is 11, which is a momentary state and will automatically turn to 00 state.　
Output signal frequency: When pin ⑧ (FADJ) = 0V, Rin is the resistance value of pin ① and pin ⑩ in series in W1, and C1 can be selected between 20pF and 100μF. Adjusting W1 can continuously change fo; adjusting W2 can obtain frequency adjustment centered on Mao and ±70% f0, which is used to adjust the frequency in a smaller range. In the circuit, Cf = 1nF, and the circuit shown in Figure 2 can obtain a sine wave from several hundred Hz to several tens of kHz.