[sdiy] triangle core VCO comparators

[Richie Burnett]

Some op-amps have anti-parallel protection diodes between the two inputs. Not a problem in typical op-amp circuits where negative feedback keeps both inputs at almost the same potential during normal operation. But it causes problems in "comparator" service where there could be considerable voltage difference forced between the two inputs!

-Richie, 

Sent from my Xperia SP on O2

---- Rick Jansen wrote ----

>This month's (March/April) NL Elektor has an article on the difference between actual comparators and opamps. True comparators are (much) faster, and can reach rail voltages, and so not rely on the amplification factor of the opamp. Also, the output stage of many opamps is not suited for comparator functions, and can even damage them.
>
>The end of the article refers this document: http://encon.fke.utm.my/nikd/latest/sloa067.pdf
>
>Bruce Carter : opamps and comparators , don't confuse them.
>
>R.
>
>> On 18 Feb 2016, at 01:48, Chris McDowell <declareupdate at gmail.com> wrote:
>> 
>> howdy, 
>> 
>> I'm wondering about the choice of comparator for triangle core VCOs. I've seen it done a few ways, like Thomas Henry's discrete comparator, or the LM311 in J3RK's (STROH Modular) VCOs on Muffs, and my own builds just use TL07x and work -pretty much- great. But I'm wondering what the experiences and preferences are of you here on the list. Fast op amp? Real comparator? Doesn't matter? I'm aware that it only matters as much as HF-Tracking matters, but I'm interested in opinions anyway. 
>> 
>> Cheers!
>> Chris
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