Datasheet for 3038 fuction generator

[Alun]

Please can I have the datasheet for the 3038 function generator project. I'd like to know the formulas used to design this circuit so I can re-design it to suit my needs and hopefully make it better too. Thanks.

[audioguru]

Hi Alun,
www.datasheetarchive.com call this an obsolete product. Years ago Intersil had some pretty good application notes about this IC.
http://www.datasheetarchive.com/semiconductors/download.php?Datasheet=933735

[Alun]

I had a feeling this was the case is there a sutable equivalent IC or some other simple way of building this signal generator?

[audioguru]

Hi Alun,
Maxim have an extremely expensive one that goes up to 20MHz, MAX038.
EXAR had theirs but don't make it anymore.

I made and have 3 sine-wave generators:
1) A Wien bridge with a calibrated frequency dial and a dual tuning capacitor from an old tube (valve) AM radio. Its output bounces when the frequency is changed and its response drops off a bit at both ends of the dial because I couldn't match its 40M resistors and capacitance of the range switch very well.
2) An extremely low distortion oscillator that I designed to have a variable frequency, but its PLL caused phase jitter that ruined its low distortion. It has a CD4018 as a stepped sine-wave maker followed by a switched-capacitor 4-stage Butterworth lowpass filter IC.
I now use it with a fixed frequency but its frequency could be changed with a single pot with a switch selecting its decades. Its distortion at the high end of each range would be fairly low.
3) A phase-shift oscillator with a very stable output level, fairly low distortion and frequencies from 20Hz to 2kHz, and 200Hz to 20kHz. I had to use a triple gang pot from a RadioShack thingy and luckily it had 4 of them for me to select the one with the best tracking. I had to order a fairly high frequency (37MHz GBP) MC33077 dual opamp for it 'cause an MC33172 opamp had way too much phase shift at 20kHz. Even an MC34072 wasn't good enough.

Fairchild has a fairly new sine-wave generator IC. Its output supposedly looks like and sounds like it has very low distortion but measuring it shows its conflict in its phase-accumulator. Its output is very stable.

Interested in a schematic?

[Alun]

I was concerned I'd have to build something as complex as 1 & 2, I did consider 3 but I don't have any triple ganged pots, can you still buy these?

Luckily I've found an old 3038 lying around at work, but I'm still very  interested in fairchild's IC (and any other possible alternatives) though just in case the IC I've found is a dud.

[hotwaterwizard]

http://www.web-ee.com/Schematics/Function%20Generator/function%20generator.htm

[Alun]

Thanks hotwaterwizard, it look like I might have to do some more design work to get this working to my specfication but good idea none the less, do you know where you can buy the MAX038 IC from? Note I live in the UK.

[audioguru]

Hi Alun,
If you are nice to Maxim, they might ship you a free sample.

[hotwaterwizard]

Exactly what are you trying to do?

CHECK OUT THIS!
http://www.digisound80.co.uk/digisound/modules/80-18/80-18.htm

[Alun]

I want to build a reasonable quality sine wave generator variable from 10Hz to at least 100kHz (the higher the better). This frequency range is very useful for testing audio amplifiers,even though the high frequencies are abouve the human hearing range they are still very useful as you can see phase shifts which occur at these frequencies  and can  cause instability and oscillation.