vco 10mhz

You can use IC 8038

its max freq is 300KHZ

hello my friend you can use max038 its the only ic which will give you 10 and 20Mhz. i am constructing a function generator with that. i bought it from http://www.futurlec.com/cgi-bin/search/search.cgi. or you can use dds technology. i hoped i helped you. (dds offers better sine wave purity).

Another approach, you could build some sort of simple voltage controllable pulse generator that goes from 20-40 MHz, divide it by two with a flip-flop to get a 10-20 MHz square wave, and then feed it through a low-pass filter that passes everything up to 20 MHz and blocks everything above 30 MHz.

Hi. Look here:
\http://www.analog.com/en/subCat/0,28...0%255F,00.html

Best Regards.

I haven't seen any DDS chips with voltage-controllable frequency (VCO). Do they exist?

DDS generate sinewave digitally,no need to analog VCO!

I tested AD9834 DDS(50MHZ DDS from ADI) (for up to 12.5MHZ sine wave)

But it have many noise in output ,there is also clcok sine wave in out put!

I placed a passive LC filter at out put but the clock harmonic will remained!


MAX038 is not recommended for new designs and is absolote!

In my opinion, for a low cost sine wave oscillator use low cost TCXOs. Some of them produce 10 MHz pulse trains. If it's the case just put a bandpass or lowpass filter after that.
Anyway discrete configurations are also very easy to implement in this freq.

If you can use an NCO instead of a VCO, that's great! A DDS can make a pretty good sinewave.

If your AD9834 circuit is outputting lots of weird harmonics and clock feedthrough, then your LC filter probably needs improvement. It needs to strongly attenuate the clock frequency and above. Be sure to use good RF construction techniques.

I used 5th order butterworth LC network but it does not remove clcok harmonic(50MHZ clcok for DDS AD9834)

My LPF 3db corner freq is 12MHZ.

My RF PCB is also good and I designed it carefully.


(I want ADJUSTABLE source and stable in freq )

A 5th order butterworth should attenuate the clock by over 60dB. If it doesn't, then something is wrong with the filter.
Or maybe the filter is working fine, and it's just a measurement problem such as a long ground lead on the oscilloscope probe.

hey!, 7rots51, did u finally could get a clean output signal from the AD9834BRUZ?, im working with this device, but at 10Mhz the outputsignal it about 200mV without any filter (when should be 600mV), is this happenned to you?