MAX083

[Tony Allgood]

Hi there,

It was scheduled to be a quiet day in the office so I decided I would have a
go at upgrading my home-made signal generator. This was based on the old LFO
idea of integrator/schmitt trigger with a few waveshapers to get some
different wave outputs. But slew rate was crap and sinewave distortion was
not good. So I bought a MAX083. Looks great on paper, both for a VCLFO or
signal generator. But beware, because it is designed to be really fast...
20MHz and up... it was a real pain to stabilise. Honks all over the shop,
couldn't get my ground clean... but then again I was using stripboard. The
sync output is real sharp edged little thing, that put glitches over the
ground and output. The data sheet warns you of this, and they are not
kidding. However, you can disable this function... and I did. Current
consumption is high (around 50mA0 and not constant either so your power
lines will be noisy without some decent filtering/decoupling. And it runs
off split rail 5 volt, not exactly handy for me I can tell you. Be careful
if you decide to have a selection of timing caps to switch in. The
inductance in the leads to the switch will cause instability of the sine and
triangle outs. Not the square though. Very fussy of output load as well. For
our purposes you will need a voltage follower/amplifier of some sort.

In the end it makes a nice sig gen with a very good sinewave. The mark/space
can be changed for all the output waveforms with only a small change in
frequency. As for VCLFO it may be useful, with a control range of 300:1.

Regards,

Tony Allgood, Cumbria, UK

e-mail: oakley at techrepairs.freeserve.co.uk

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