To use TLV521 as a comparator that need notice something?

Chen Bogey8

Mastermind 9990 points

Other Parts Discussed in Thread: TLV521, LM339

Hi sir

we choice TLV521 to as a comparator due to low cost, small package, low power nanopower and circuit as below.

Is there something we need notice? and TLV521 seems have no Hysteresis spec. is it suit to be comparator?

over 9 years ago

0 Paul Grohe over 9 years ago

TI__Guru 62826 points

Hello Chen,

The TLV521 is an operational amplifier, not a comparator, so it would not have a hysteresis specification. Internal hysteresis would not be good for an op-amp.

The TLV521 can be used as a comparator, but external hysteresis needs to be added.

Op-Amps generally make poor comparators, and we generally discourage the practice, but there are situations where they are suitable.

Beware, that without hysteresis, the output will chatter as the input slowly approaches the threshold. An op-amp, since it has a linear (not digital) output, can oscillate or float at some random voltage between 0 and 3.3V.

See the following blogs:

https://e2e.ti.com/blogs_/archives/b/thesignal/archive/2012/03/14/op-amps-used-as-comparators-is-it-okay

https://e2e.ti.com/blogs_/archives/b/thesignal/archive/2013/01/28/comparators-what-s-all-the-chatter

Also see AN-74. While it is about the LM339, the hysteresis concepts are the same:

http://www.ti.com/lit/an/snoa654a/snoa654a.pdf

The op-amp has a push-pull output, so it does not require the pull-up resistor (R80).

Regards,

Amplifiers

Amplifiers forum

To use TLV521 as a comparator that need notice something?