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 Forum index » DIY Hardware and Software » Thomas Henry designs
Wider Range LFO
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Thomas_Henry



Joined: Jul 24, 2009
Posts: 139
Location: N. Mankato, MN

PostPosted: Thu Jan 22, 2015 10:55 pm    Post subject: Wider Range LFO
Subject description: 0.10 Hz to 100 Hz
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Hi Gang,

Here's another simple LFO, but with an improved range. It can be used from 0.10Hz to 100Hz, a sweep ratio of 1000:1. At the low end, that's one cycle every 10 seconds. It's a two-chip design.

The two trimmers set the lowest and highest frequencies at the extreme throws of the Rate pot, adding a trifle to the repeatability of the thing. It's nice to know where you're at when setting a pot position, especially in powers of ten. The trimmer on the low end also guarantees the control current never drops below 1uA which would cause the LFO to stall.

Outputs are the usual standard +/- 5V, with an impedance of 1K.

Oh, the essential core of the thing is straight from the LM13700 datasheet.

Thomas Henry


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J3RK



Joined: Jun 05, 2006
Posts: 107
Location: Seattle

PostPosted: Tue Jan 27, 2015 11:22 am    Post subject: Reply with quote  Mark this post and the followings unread

Would the little CV section from this circuit work to allow voltage control? It's a little VC integrator thingie I use for PLLs. I typically just use a simplified triangle core VCO (ala EN, VCO-1, etc.) for my LFOs, but am just curious.

I was also thinking a little PWM comparator off of the triangle could be fun too. Nice LFO!

The lower half of this pic contains the CV circuit I mentioned:

Posted Image, might have been reduced in size. Click Image to view fullscreen.
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