Please, someone who happens to know, reply to this simple question, yet google.com couldn't link to an answer!
I am building a PCB for LM3886 amplifier but I have no idea how I must connect the input electrolytic capacitors.
Which capacitor terminal, anode or cathode should be connected to the non-inverting input? A 1k resistor is between user input and non-inverting terminal, a 22k resistor is between user input and ground. The capacitor will be connected to user input. Which capacitor terminal goes there?
Google is only good to give adverts and links to buy ready made products.
I am building a PCB for LM3886 amplifier but I have no idea how I must connect the input electrolytic capacitors.
Which capacitor terminal, anode or cathode should be connected to the non-inverting input? A 1k resistor is between user input and non-inverting terminal, a 22k resistor is between user input and ground. The capacitor will be connected to user input. Which capacitor terminal goes there?
Google is only good to give adverts and links to buy ready made products.
> google.com couldn't link to an answer!
> Which capacitor terminal, anode or cathode should be connected to the non-inverting input?
First G-hit is the LM3886 data sheet, font of all wisdom.
It obviously depends if you are powering bipolar supply or single supply.
For single supply Fig 3 is your guide.
For bipolar supply, look at the basic operation. Both inputs should sit at "zero" DC. The datasheet doesn't even use capacitors. I'm paranoid so I like caps. With near-zero DC voltage a Film cap would be preferred; electros like some steady DC on them. However modern electros don't need it so much. Bi-Polar electros are available. However for the expected <1V DC here, plain electros will work *either way*. (It takes more than a Volt of reverse bias to break down.)
Finally, study the Internals, page 7. The inputs are NPNs. If you connect a resistor to zero-volt ground, the base current will drift the bases slightly -negative-. This can guide your cap polarity. How much? Input bias current is as-much-as 1uA. Given 22k resistor, this is 22mV.
> Which capacitor terminal, anode or cathode should be connected to the non-inverting input?
First G-hit is the LM3886 data sheet, font of all wisdom.
It obviously depends if you are powering bipolar supply or single supply.
For single supply Fig 3 is your guide.
For bipolar supply, look at the basic operation. Both inputs should sit at "zero" DC. The datasheet doesn't even use capacitors. I'm paranoid so I like caps. With near-zero DC voltage a Film cap would be preferred; electros like some steady DC on them. However modern electros don't need it so much. Bi-Polar electros are available. However for the expected <1V DC here, plain electros will work *either way*. (It takes more than a Volt of reverse bias to break down.)
Finally, study the Internals, page 7. The inputs are NPNs. If you connect a resistor to zero-volt ground, the base current will drift the bases slightly -negative-. This can guide your cap polarity. How much? Input bias current is as-much-as 1uA. Given 22k resistor, this is 22mV.
PRR said:
Code:
$ dict paranoid
3 definitions found
From The Collaborative International Dictionary of English v.0.48 [gcide]:
paranoid \par"a*noid`\, a.
1. (Med.) Affected with paranoia; as, a paranoid
schizophrenic.
Syn: paranoiac.
[PJC]
2. Suffering from delusions of being persecuted by the
conspiratorial actions of others; having an unwarranted
suspicion of the motives of others; -- used loosely in a
negative sense, not as a medical term; as, just because
you're paranoid doesn't mean they are not out to get you.
[Colloq.]
[PJC]
From WordNet (r) 3.0 (2006) [wn]:
paranoid
adj 1: suffering from paranoia
n 1: a person afflicted with paranoia [syn: {paranoid},
{paranoiac}]
From Moby Thesaurus II by Grady Ward, 1.0 [moby-thesaurus]:
25 Moby Thesaurus words for "paranoid":
brain-damaged, brain-injured, catatoniac, catatonic, certifiable,
certifiable case, disturbed, manic-depressive, mental, mental case,
mentally ill, mentally sick, neurotic, paranoiac, psycho,
psychopath, psychopathic, psychopathic case,
psychopathic personality, psychotic, schiz, schizo, schizoid,
schizophrenic, schizyI do not understand why you personally attack (try to shame) me. I am suspicious of your motives.
Attachments
Forget prejudice and have a good laugh. Life is too short. Grab a glass of your favourite drink to celebrate, for it is festive season.
YouTube
[ Note: The video illustrates situations that serious talk can sometimes be funny. This video is NOT intended to insult but to portray that possibility. ]
Nevertheless, this project, with its double size inverted LM3886 IC pads, works. I only need to add an RC filter across the load, protect the PCB's copper tracks against corrosion, and it is done.
Well Done to DIYaudio.com for its motivating company, and surprisingly, reality can be surprising, to people like PRR. Your posts made me realise an electrolytic capacitor, is not actually needed on the input of an amplifier using a split power supply. Thanks, a lot for that invaluable tip.
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His advice is good advice, and well appreciated, although I do not always like the way he writes.- Status
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