Author Topic: Op amp gentle phase fold?  (Read 2263 times)

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Offline MTTopic starter

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Op amp gentle phase fold?
« on: October 14, 2017, 11:20:08 pm »
The CA3260 and 3160 have the peculiar feature gentle phase folding while most opamps abruptly phase reverse.
is there any other opamp that does the same as CA3160?
 

Offline Benta

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Re: Op amp gentle phase fold?
« Reply #1 on: October 15, 2017, 08:15:12 am »
Do you mean that the output does not phase reverse when the input goes below the negative rail?
Quite a lot of opamps have this, I've seen several from NSC and TI. It has to be specifically mentioned in the datasheet.
 

Offline MTTopic starter

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Re: Op amp gentle phase fold?
« Reply #2 on: October 15, 2017, 06:48:34 pm »
Unipolar supply.

Phase reversal




Phase folding:
 

Offline Audioguru

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Re: Op amp gentle phase fold?
« Reply #3 on: October 15, 2017, 09:11:44 pm »
The datasheet for the CA3160 says that it does not reverse the phase when its input goes 7.5V below ground when it has only a positive 15V supply.
Its common mode input voltage range is -0.5V to +12V with a single +15V supply. 
 

Offline Benta

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Re: Op amp gentle phase fold?
« Reply #4 on: October 15, 2017, 09:17:48 pm »
This is all fine, but I still don't understand what the question is.
Perhaps MT could enlighten us?
 

Offline mikerj

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Re: Op amp gentle phase fold?
« Reply #5 on: October 16, 2017, 11:13:52 am »
This is all fine, but I still don't understand what the question is.
Perhaps MT could enlighten us?

Seems pretty obvious, he is asking if there are any other op-amps that display the same phase characteristics as the CA3260 when the common mode range is exceeded.  I don't know of any myself.
 

Offline MTTopic starter

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Re: Op amp gentle phase fold?
« Reply #6 on: October 16, 2017, 01:44:01 pm »
Mikerj nail'ed it! :)  There are some old PNP amps that also folds but does it ugly. Phase folding is a natural transistor phenomenon.
« Last Edit: October 16, 2017, 02:02:51 pm by MT »
 


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