[sdiy] Logic to +/-5V conversion

[Tim Ressel]

So here I am laying out the 4053 solution when it occurs to me that I 
can run all the logic on +/- 5V. I have LM311 comparators turning analog 
into digital but those can do +/- 5V outputs as well. That should give 
me my bipolar outputs without having to massage the levels.

Or am I missing something?

--TimR

On 11/21/2015 1:14 PM, rsdio at audiobanshee.com wrote:
> On Nov 21, 2015, at 5:58 AM, Simon Brouwer <simon at brousant.nl> wrote:
>> Opamps in general are not the best choice for this unless you select a rail to rail output type (assuming you have -5 and +5 rails).
> Agreed, with a couple of caveats regarding my original response.
>
> First, I assumed that +/-12V is available (Doepfer modular), so +/-5V would not be an issue at all for a standard op-amps.
>
> Second, I somehow missed that Tim only wants to output +5V and -5V exactly, and not anything in between! For binary output, an op-amp is a bit overkill, although it will provide the proper voltage to just about any load.
>
>
>> I would use LM339 which is a low cost quad comparator. It has open collector output though, so you need pull-up resistors.
> Good suggestion, but the pull-up voltage will sag when high currents are sinked by the load. When the output is -5V, though, the voltage will be consistent under any normal load.
>
> I tried to come up with a simple, two-transister FET solution with a complementary pair of depletion-mode PFET and NFET transistors, but it looks like the task requires three or more transistors to work.
>
> Brian
>
>> Best regards
>> Simon
>>   
>>
>>> Op 21 november 2015 om 2:49 schreef rsdio at audiobanshee.com:
>>> Doing it with op amps IS the clever way. But I think that pulling it off with a single op-amp, as opposed to a dual, is the cleverer way. I recently worked this out for +/-10V, but I can't find the paper where I scribbled down the notes.
>>>
>>> There's a DAC data sheet out there with the 0-5V to +/-5V op-amp circuit in it as an example of interfacing their DAC. Forgot who that was, but sounds like you already have that circuit.
>>>
>>> Brian
>>>
>>>
>>> On Nov 20, 2015, at 4:51 PM, Tim Ressel <timr at circuitabbey.com> wrote:
>>>> Hi y'all,
>>>>
>>>> I'd like to take several 0-5V digital lines and make them swing +/-5V. I can do it with op amps, but is there a clevererer way?
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-- 
--Tim Ressel
Circuit Abbey
timr at circuitabbey.com