puzzle on op-amp type comparator driving capability

[hsiangleung]

how to understand the op-amp type comparator driving capability? it is said that current mirror amplifier, when used as a voltage comparator, has equal driving capability for both high and low outputs. what does it mean? what about other amp, i.e telescope amp?

can anyone explain it? thanks!

 

[KlausST]

Hi,

I'm not sure what you mean...

Often comparators have open collector or open drain outputs, that can drive only low side.

Amplifiers usually have totem pole outputs, that can drive to both supply rails.

Klaus

 

[hsiangleung]

hi Klaus,

thanks for your kind reply. In another word, op-amp type comparators often have different rise and fall time, is that to say they have different driving capability for high&low outputs? If so, what's the reason behind it and why current mirror amplifier has equal driving capability?

thanks&regards

hsiangleung

 

[KlausST]

Hi,

google for "totem pole", "open collector" and "open drain".

If you read through this you will find the answers.

Klaus

 

[hsiangleung]

hi Klaus,

your suggestion is really helpful, thanks a lot.

Hsiangleung

 

[fightshan]

Usually, an op-amp will not be used to drive load directly when used as a comparator, for example, if a comparator is used to drive a large capacitive load,a push-pull output stage is necessary for the op-amp.
You told "it is said that·····", what is your reference?