This datasheet has been download from: Datasheets for electronics components. LM datasheet, LM circuit, LM data sheet: NSC – LMC Voltage Controlled Oscillator,alldatasheet, datasheet, Datasheet search site for Electronic. LM National Semiconductor datasheet pdf data sheet FREE Datasheets (data sheet) search for integrated circuits (ic), semiconductors and other electronic.

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Does this affect the frequency change you observe in any way? If you only need a low frequency VCO, this is the easiest way to build one. Capacitor C2 is used to prevent the parasitic oscillations during VCO switching. The IC has a very linear modulation characteristic and has excellent thermal stability. This depends on what level of accuracy you need. It’s not a perfect sinewave by any means, but it’s quite acceptable for frequency response scans. The output frequency vs.

The resistors around the input are designed to ensure that the positive and negative integration times are identical, hence R3A and R3B in parallel because the exact half value isn’t available in most resistor series.

Greater frequency range is possible with careful design. The circuit diagram of a voltage controlled oscillator using LM is shown in the figure below. Most Active Software Boards: Here a varactor varicap diode is used in place of the capacitor in the tank circuit.

LM Datasheet pdf – LMC Voltage Controlled Oscillator – National Semiconductor

The 2SC appears to be an older component and may be hard to come by sim and layoutbut there are several medium power transistor replacements that might work and there are several available in the Multisim database. Signal Generatorsvcovoltgae controlled oscillator. FiddyOhm first of all i’m sorry my english isn’t that goodwhat i meant was the frequency keeps changing even though the control voltage is constant i haven’t even started to vary it yet.


The advantage of circuits like those shown here is that there are no glitches in the output, no matter how quickly or slowly the frequency is changed. The VCO can be operated from a dual supply, and that only entails a few minor changes.

The author Rod Elliott grants the reader the right to use this information for personal use only, and further allows that one 1 copy may be made for reference while constructing the project. Sign up using Email and Password. Message 6 of 7.

See below for the diode clipping circuit. The block diagram of a typical voltage controlled oscillator is shown below. VCOs are used for tone generators, frequency modulators, clock generators, function generators, music synthesisers and frequency shift keying FSK, a radio transmission system where digital information is transmitted via discrete frequency changes of a carrier wave.

Can you recommend a circuit or teach me how to do this?

By clicking “Post Your Answer”, you acknowledge that you have read our updated terms of serviceprivacy policy and cookie policyand that your continued use of the website is subject to these daasheet. If the source circuit is direct coupled, it must be capable of providing some current.

Sensitivity is halved because the effective supply voltage has been doubled compared to the single supply version shown in Figure 2. Unfortunately, the NE or LM which was dataasheet equivalent is no longer available from any reputable supplier.

Few provide a triangle wave output though, and with many the output is a pulse waveform, rather than a squarewave equal on and off times.

Voltage Controlled Oscillator (VCO)

It can be used to generates square and triangle waveforms simultaneously. As shown, four diodes are used to clip the triangle wave in such a way as to get minimum distortion. R6 and R7 set the threshold, which is also affected by eatasheet output voltage from U1B. However, using a 2N or similar may improve the satasheet symmetry very slightly because it has a lower on resistance than a bipolar transistor.


An active element like a transistor is used for amplifying the output of the LC tank circuit, compensating the energy lost in the tank circuit and for establishing the necessary feedback conditions. This will change slightly depending on the load and the ICs internal temperature. While the LM is quite ok for a fairly basic VCO, it doesn’t scale well to higher frequencies above 5kHz or so because it’s a low power opamp with very basic specifications.

However, the supply voltage must be regulated, or the amplitude of the two outputs will vary with the supply voltage. Message 2 of 7. I also want to know Saud Khan. If these aren’t high on your list of features then much simpler VCOs are easily constructed using a timer or similar.

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. You may also like: The output frequency can be also programmed using a set of external resistor dstasheet capacitor. However, the frequency also depends on the threshold voltages for the Schmitt trigger U1B. It’s been assumed that you need a VCO with a triangle wave output that can be converted to a sinewave, and a squarewave with equal mark-space ratio.