I've been looking at comparators recently, never having used the much before, and have become slightly baffled by how much there is to consider.. should have known

I was using open collector types but I found it incredibly difficult to get the results I needed - im looking to compare two signals between +-10V and produce a 0-5V output. The output needs to transition from 0-5v in under 1uS - faster would be better, but not if it results in a considerably more expensive device or one that has more exacting requirements for avoiding oscillation, driving loads etc. I didn't think this would be a hard thing to do, that I could pretty much get a high slew rate op-amp, but when operating the op-amp as a comparator i have to go rail-to-rail, which would mean running of +-12v, which slows the transition considerably, and when you get above 20v/uS ive just been finding internally compensated op-amps that only work at unity gain. TL052 would just about do it as the *typical* slew rate is rated at something like 22V/uS but the *minimum* is actually 11V/uS. The device must also be available in DIP / through hole package. I tried using open collector comparators but had no end of problems driving loads without them producing oscillation at the output, plus i need the low to high and high to low transition to both be sharp and of roughly the same time.

so to recap, im looking for a comparator (or op-amp if one fits the bill) that I can use to compare two signals between +10V and -10V, will transition in under 1uS, that is cheap (£1.50/$1.88 being the limit), available in a through-hole package, NOT open collector, relatively stable driving loads - something that just is not going to cause me unnecessary grief

 

If you can live with the output arrangement (see Fig. 5 on page 10) and USD 1.25/k this: http://cds.linear.com/docs/en/datasheet/1011afe.pdf might do it for you.

Just for grins, what power supply voltages will you be using, what's the source impedance of your comparator's +/10 volt inputs, how fast will they be, and what does the comparator's output have to drive?

 

Hi, that one is an open collector type, no? I would like to avoid open collector types as they use unnecessary power, don't have even up/down transitions and seem to freak out (lots of chatter in the transitions) when I load them with almost anything!

The source impedance is an op amp, but I was filtering the inputs with a 10K resistor and a 1nF cap. Not sure what you mean by how fast will they be? You mean frequency? its audio stuff... the output of the comparator needs to be ac coupled, or drive a diode and then ac coupling (i mean a series cap and resistor to ground)

 

Hi, that one is an open collector type, no? I would like to avoid open collector types as they use unnecessary power, don't have even up/down transitions and seem to freak out (lots of chatter in the transitions) when I load them with almost anything!

The source impedance is an op amp, but I was filtering the inputs with a 10K resistor and a 1nF cap. Not sure what you mean by how fast will they be? You mean frequency? its audio stuff... the output of the comparator needs to be ac coupled, or drive a diode and then ac coupling (i mean a series cap and resistor to ground)

To me, this seems to be getting more and more confusing, so rather than just exchanging opinions, would you please post a schematic of what you have and a verbal description of what you want your widget to do?
Thanks.

 

Hi, that one is an open collector type, no?

Until recently, all comparators had open collector outputs.

don't have even up/down transitions

Look for one that doesn't have OC output.

seem to freak out (lots of chatter in the transitions) when I load them with almost anything!

"Chatter" shouldn't be dependent on load. If the comparator is switching, it's either due the inputs causing it to switch or it's oscillating.

 

yeah, i don't know why it's chattering but at the moment im not interested in the reason why - maybe when i have a little more time. For the other reasons i mentioned im just looking for a different device

 

The output needs to transition from 0-5v in under 1uS - faster would be better

its audio stuff

Why do you need such a fast response for "audio stuff".
That makes little sense.

If you tell us exactly what you need to do, rather than the specific problem you have, we can likely give you better help.

 

I actually said that the INPUT was audio. I am working with digital processing so time makes a big difference

but im just interested in suggestions for devices. Thanks!

 

I actually said that the INPUT was audio. I am working with digital processing so time makes a big difference

but im just interested in suggestions for devices. Thanks!

If you'd attenuate the input audio signals to the comparator via a pair of voltage dividers, a little due diligence on your part would likely find a device to suit your needs.

BTW, a verbal description of what you're trying to do and a schematic of what you have now - which doesn't work - would help us help you.