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The frequency modulation is clearly visible, as is the wave shape. A positive modulation voltage causes the frequency to increase, and vice versa. The base frequency can be set by a pot as shown, and the modulation signal is symmetrical around zero volts. If the triangle output is at zero, the square output will be at around 10V and vice versa.
The output frequency can be also programmed using a set of external resistor and capacitor. If these aren’t high on your list of features then much simpler VCOs are easily constructed using a timer or similar. Since you can’t get the NE or any equivalent any more, if you want or need a VCO you have to build it using opamps.
This is engineering, not poetry. The output frequency of the VCO can be obtained using the following equation: It isn’t designed for audio use, and has higher distortion lm566 most other opamps. Resistor R3 is used to provide the control voltage Vc. The datasheet shows a formula for frequency, and with the values given in Figure 1 it works out to be 1kHz if the ‘Set Base Frequency’ pot is set for 6V.
It’s important to connect the input stage including the transistor as shown. The next circuit will do just that, but it’s not a precision circuit.
LM National Semiconductor, LM Datasheet
Email Required, but never shown. Despite appearances, the input will not be at zero volts when the pot is centred. Message 7 of 7.
See below for the diode clipping circuit. As shown, four diodes are used to clip the triangle wave in such a way as to get minimum distortion. One application that can be very useful is to use a VCO as a sweep generator for testing loudspeakers, crossover networks, equalisers, etc. The output voltage may be stuck at zero or around 10V. Because most are unable to pull the output voltage down to the negative supply, we need datashete add an extra resistor R9, Figure 3 to ensure that the lm566 Q1 will turn on and off properly.
pll – LM Frequency deviation problem – Electrical Engineering Stack Exchange
Better performance may be available from a TL or any other reasonably fast opamp. Changing the Schmitt trigger resistors will change the output level of the triangle wave, which will affect the distortion when the diode clipper is used to obtain a sinewave. Also your link is to the lm566 your title and text says Here a varactor varicap diode is used in place of the capacitor in the tank circuit.
You’ll find countless examples of this circuit on the Net, but since you will be unable to get a reliable source of the ICs it’s a moot point. Commercial use is prohibited without express written authorisation from Rod Elliott.
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You can also change the resistors around the input stage or the Schmitt trigger. The frequency changes on its datashdet accord. While using a single supply, the supply voltage range is from 10V to 24V.
Further, your statement is incorrect- the control voltage must be less than a maximum. This isn’t needed for the LM, but is required for many other opamps that are a great deal faster.
If the exact ratios are not maintained the waveform will become sawtooth, with different positive and negative going times. If the source circuit is direct coupled, it must be capable of providing some current. Your email address will not be published.