High frequency sine wave generator.

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Has anyone any suggestions for a 'high' frequency sine wave generator circuit?
Variable frequency, 100 kHz to 10 MHz approximately.
Output level not critical, ideally variable up to say 1 V rms.
Distortion not critical, ideally < 1% total harmonic distortion.
Cheap.

I can't think of any options other than spending money on a function generator or arbitrary wave form generator.

I have prototyped an Electrostatic Direct Drive amplifier and have tested the open loop gain to 100 kHz but I really want to test the open loop gain and phase response at higher frequencies. I have thrown together an operational amplifier based Wein bridge but it's not great and only gets up to around 1 MHz. I have searched for function generator circuits without success apart from the obsolete Maxim and Intersil offerings. Designing and building a function generator that can reach 10 MHz with a reasonable sine wave doesn't seem to be easy.
 
One easy way, although I don´t know if can be a solution for your request may be, to make an RC oscillator using a 74HC04, or any similar. Then, pass the squeare output by a LC multi-section to get a sinusoidal waveform, such filter mus be a couple decades below the RC frequency. The trouble that it is difficult to sweep, because the signal level will vary with frequency.

A best variant may be a PLL with a 4046, and then filter in the same way as above.
 
Wavetek made various function generators like the 185 that went to 5 MHz, and more that went higher. Download a manual with schematics to see how they did it. IIRC, they used current sources to make simple discrete oscillators that performed very well, then the usual rounding circuits to make the sine waves with about .2% THD. No doubt modern 1-chip solutions would get you there quicker, but the discrete solutions are simple and use no special parts. Also look at the ARRL handbook for various oscillator solutions.
 
Hi,

Probably the easiest way to do sine wave between 0-10MHz (and more) is to use a DDS
synthesizer IC. If you have some knowledge in micro-controller programming, you can do all by yourself. Otherwise, you can buy one already build from many different source.
You can look this one, it seem interesting for your needs(but limited to 5MHz).
Also this one, up to 20MHz.
Regards.

Frex
 
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Thanks to everyone for their inputs. I am considering the various options.

Unfortunately the MAX038 is obsolete so I am not keen to use it.

In the UK/Britain/England second hand test equipment is expensive because of lack of supply. In my experience the UK electronics industry is small and has low budgets for buying stuff. Stewart of Reading list an HP3312A at £ 175.00 and a Wavetek 185 at £ 150.00. I don't really want to spend money on 20 to 30 year old stuff that could have reliability problems when new equipment (from TTI, not best quality though) isn't that much more expensive.
Thanks for the suggestion of looking at the Wavetek 185 schematic. I have downloaded a copy but it doesn't look very easy to recreate. I only want a limited frequency range and sine only which does simplify the circuit a bit though.

I have used varicap diodes with crystals for frequency trimming and with effort could make up oscillators and a mixer but I am not sure how easy that is.

I might just splash the cash on something new rather than spend a long time on the problem.
 
I am just concluding this thread. I have just bought a Thurlby Thandar Instruments TG1000 10 MHz DDS Function Generator. The Sine output at 10 MHz looks pretty clean on the Oscilloscope which is good enough for my requirements. I am using it to measure amplifier open loop gain.
 
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