Re: Sine generator IC solution?

From: Michael Black (et472_at_FreeNet.Carleton.CA)
Date: 01/30/05 

Date: 30 Jan 2005 18:41:05 GMT

Spehro Pefhany (speffSNIP@interlogDOTyou.knowwhat) writes:
> On Sun, 30 Jan 2005 09:12:16 +0000, the renowned John Woodgate
> <jmw@jmwa.demon.contraspam.yuk> wrote:
>
>>I read in sci.electronics.design that dave.harper
>><dave.harper@gmail.com> wrote (in <1107040148.604139.327150@c13g2000cwb.
>>googlegroups.com>) about 'Sine generator IC solution?', on Sat, 29 Jan
>>2005:
>>>Are there any variable sine generator IC's? I was looking for a single
>>>chip solution, but am not sure if they exist (other than programing a
>>>PIC or similar). The frequency range I'm working with is between 200
>>>and 2000 Hz. Ideally I'd like it to be accurate (or adjustable) to
>>>within 10 Hz.
>>>
>>Any cheap op-amp and a few passive components will do what you want. I
>>just don't understand why people propose relatively hugely more complex
>>solutions.
>>
>>Part of engineering skill is not to spend more money than necessary. In
>>fact one definition of an engineer is 'someone who can do for a dollar
>>what any other fool can do for 10'.
>
>
> An op-amp (or a few discrete transistors if you ignore the "IC
> solution" part of the OP's question) and a handful of passives and a
> nonlinear element of some kind (lamp, thermistor etc.) can be used to
> make a Wien bridge oscillator, probably the most easily adjustable
> sine-wave oscillator. But the specs might push the solution somewhere
> else. If you google on "Wein bridge" and "Wein bridge" (the latter
> has 3 times as many hits, though some may lead you to bridges over the
> Danube) you should get some good ideas.
>
Some of it surely depends on what he wants the thing for. That 10:1
tuning range may be the reason for calling for an IC, or it may just
be that he's unfamiliar with the alternatives.

One neat thing about those IC function generators is their wide continuous
range. But of course, they go do those non-traditional schemes in order
to be able to get 10:1 or wider range in one segment. If one needs the range,
one often doesn't need the purity of the sinewave. If one needs the
purity of the sinewave, they may not need continuous tuning, or at least
can live with discrete steps.

  Michael