NorthernLightX Posted January 5, 2013 Report Share Posted January 5, 2013 Hi all, in preparation of the MB6582 with redesigned AOUT, that will be configured for +/- 5V CV signals, I am looking at some circuits to put in front of existing modules that are expecting CV signals of 0v to +10v. For extra flexibility/compatibility I'd like to have the level shifting switchable, and the input CV signal attenuatable (nice scrabble word by the way :rofl: ) I have found this schematic on the MFOS website: http://www.musicfromouterspace.com/analogsynth_new/HOT_TIPS/PDF/DCCoupledLevelShifter_assembly.pdf I've come up with the following scenario: - the +/-5V input CV signal is fed to the upper input, this has an attenuator as well - a +5V signal can be switched on for the second input The only thing this doesn't yet have is protection against over voltage and negative voltage. For over voltage protection a 10V zener diode is probably the answer, but what about negative voltage? I don't want to damage the circuit behind the level shifter. Quote Link to comment Share on other sites More sharing options...
Shuriken Posted January 5, 2013 Report Share Posted January 5, 2013 Maybe this topic helps Quote Link to comment Share on other sites More sharing options...
NorthernLightX Posted January 5, 2013 Author Report Share Posted January 5, 2013 Yes that's helpful indeed! I need to invert the summed voltages anyway, so doing that with a rail-to-rail opamp could be an easy solution to do the inverting and the protecting in a single package. For the supply rails I don't have a +10V supply available but a voltage devider could be calculated for that. Quote Link to comment Share on other sites More sharing options...
NorthernLightX Posted January 6, 2013 Author Report Share Posted January 6, 2013 After re-reading some of the info on the 2164 board it seems the module is fine with a CV voltage of 11,67. I think it will handle the 0,33V over voltage as well if the "protection" opamp is powered by 12V, so no need to create a separate 10V supply. Less parts is good :thumbsup:. Quote Link to comment Share on other sites More sharing options...
NorthernLightX Posted January 6, 2013 Author Report Share Posted January 6, 2013 I'm searching for a good single supply rail-to-rail opamp for the voltage follower. LM324 is a cheap choice but performance is not so good, I've read it can't go all the way down to ground, so +0,3V is the lowest you can go with it. MC3403 is an alternative, but I can't find if the performance at ground is much better. Suggestions are welcome. Quote Link to comment Share on other sites More sharing options...
Shuriken Posted January 7, 2013 Report Share Posted January 7, 2013 What is wrong with the TLV274? Quote Link to comment Share on other sites More sharing options...
NorthernLightX Posted January 7, 2013 Author Report Share Posted January 7, 2013 (edited) What is wrong with the TLV274? Reichelt doesn't carry it :whistle: Anyway, I've been drawing and thinking and some more drawing and I think I have a solution that does not require a rail to rail opamp. One schottky diode as a negative voltage protection is sufficient. Proposed schematic and board: (Pad1 and Pad2 are there to accomodate different pin space potentiometers) Edited January 7, 2013 by NorthernLightX Quote Link to comment Share on other sites More sharing options...
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