This is a Digital logarithmic sweep signal generator circuit by using the average digital. It uses together with the frequency generator by voltage controller.
How Digital logarithmic generator works
In the circuit, the 14-bit binary counter circuit, that input is synced with the output of oscillator generator circuit. Then, the 8 output of IC-4020 is connected to the resistor networks, that will change the digital code to the DC voltage level.
Thus, the DC voltage level from zero to about 0.2Vb. So it is divided into 256 steps. But lower output will not connects to any things. It cause the DC voltage level Uo increased step by step. After that, the clock through 128 cycle. This output can continue to sweep input of the oscillator is controlled by voltage.
A frequency generator from the circuit (And frequency synchronization output) increases every time the control voltage increases. This makes the voltage and frequency increased almost as exponential required.
When applying Uo from the oscillator controlled by voltage into Vin of this circuit. The resistor R9 the t input of IC2 must change to direct connect. Thus no logarithmic voltage at Uo, But it is only the output of IC2.
The circuit connecting
The circuit will connect two sections in together with adjusting as follows. To connects the reset wire to connect temporarily reset to IC4020, across reset pin to a positive voltage. Then, adjust the frequency at pin 11 of XR2206 take output is 80Hz.
Next, Disconnect the reset wires from the positive to ground instead. Then, adjust start bottom to “connected” the sweep frequency (the clock frequency of IC1) will start at lowest frequency (80 Hz) and long times about 1 Second. After that, the IC1 will increase the frequency in step by step until you reach 20 KHz.
The speed of sweeping can increase is 2 times, by connected to resistors R1 to R8. In the sweeping circuit, Q6 to Q13 replace output Q7 to Q14 and If move to Q5 – Q12 instead will can get speed up to 2 times. The speed of the basic clock can multiply with 8 by connecting output Q4 to Q11.
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