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What is the meaning of an negative amplifier?

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Nigel Goodwin said:
It means it's an attenuator, and NOT an amplifier.
Ummm...
An attenuator has gain between zero and one. Negative gain means the signal is inverted from input to output. Nigel, I think you had a brain fart.
 
Nigel Goodwin said:
Depends on how it's specified - I was presuming negative gain in dB's - but I take your point, the question wasn't very clear (and still isn't!).
Good point(s). I had brain constipation.
 
Ron H said:
Good point(s). I had brain constipation.

We were just reading the same question differently - sometimes it's hard to write a question (even one as simple as this) and make it unambiguous. That's why it's important to give full details about what you're asking and why!.
 
Nigel Goodwin said:
Depends on how it's specified - I was presuming negative gain in dB's - but I take your point, the question wasn't very clear (and still isn't!).

But Nigel, you are always decrying dBs!!!!

What was it you quoted from one of your former lecturers....

"Only those who dont know wat they are talking about use dBs":D :D :D

JimB


A merry xmas to all our readers, except the lazy students.
Oh hell, merry xmas even to the lazy students.
 
JimB said:
But Nigel, you are always decrying dBs!!!!

What was it you quoted from one of your former lecturers....

"Only those who dont know wat they are talking about use dBs":D :D :D

JimB


A merry xmas to all our readers, except the lazy students.
Oh hell, merry xmas even to the lazy students.

Watt is your final answer?!?

;)

This question can be taken both ways.
 
I see...thanks so much for the replies,guys...I've thought that it's somehow related to the inverted output (180 degrees shifted)...thanks so much for the confirmation :)
 
Isn't the phase shifting just called an inverting amplifier? Calling that negative gain is a really poor usage of the word.
 
Sceadwian said:
Isn't the phase shifting just called an inverting amplifier? Calling that negative gain is a really poor usage of the word.
That's your humble opinion, right? ;)
 
I thought a negative amplifier (or an amplifier with a negative gain) means it does invert the signal? Maybe I am incorrectly correlating negative amplifier with negative gain?
 
There is no such thing as a negative amplifier nor negative gain.
The amplifier either has gain or attenuation and its output is either inverted or it is not.
 
I mean like when the gain of a buffer IC is listed as -2 in a Maxim datasheet- not as an actual term used to describe amplifiers. Is the OP talking about what it means when the gain for an amplifier is listed as a negative number? Or when someone says "negative gain" when talking about an amp?
 
Last edited:
Negative gain is a commonly used term for the gain of an inverting amplifier. Google "negative gain".
 
There is no need for confusion about negative gain.

If an amp has a gain of 3 and you input a signal of say 2 sin (wt) then the output is 6 sin (wt).

But, if an amp has a gain of -3 and you input a signal of 2 sin (wt) then the output is -6 sin (wt).

Which can be expressed as 6 sin (wt + x) where x = Pi which is 180 degrees, ie. a phase shift of 180 degrees.

If the gain is expressed in dB, then a gain of -5 dB is in fact a loss of 5 dB.
 
audioguru said:
There is no such thing as a negative amplifier nor negative gain.
The amplifier either has gain or attenuation and its output is either inverted or it is not.

Sorry..it's a typo..what i meant to type is an amplifier with negative gain...Moderators, u can change the title to avoid misunderstanding. I can't edit the thread's title..

Sorry again...Thanks everyone for replying :)
 
wakiki said:
Sorry..it's a typo..what i meant to type is an amplifier with negative gain...Moderators, u can change the title to avoid misunderstanding. I can't edit the thread's title..

Sorry again...Thanks everyone for replying :)

No, the title can't be changed - you also haven't made your question any more clear?.
 
Anyway we all know it isn't as simple as having a 180° or 0° phase shift, roll of frequency and unity gain phase shift are also important fro stability.
 
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