EMRFD Message Archive 7504
Message Date From Subject 7504 2012-05-13 13:07:26 Robert Bennett Unity Gain Bandwidth Hello all,
Pardon my being so dim, but I am looking at the datasheet for the Philips
NE592 video amplifier.
It appears to say two contradictory things;
1) Unity Gain Bandwidth is 120MHz.
2) Further down the data sheet there is a graph which shows the gain at
10MHz as 45dB (Gain 1)
How are these two pieces of data reconciled?
7505 2012-05-13 14:20:19 Ken Frazer Re: Unity Gain Bandwidth Robert,
I believe you must be confusing Gain 1 with "a gain of 1." If you will note in the table on page 252, Gain 1 is actually a voltage gain of ~400 V/V, thus the graph showing 45 dB of gain at 10 MHz.
7506 2012-05-13 18:20:18 Andy Re: Unity Gain Bandwidth > 1) Unity Gain Bandwidth is 120MHz.Alternatively, the "Unity Gain Bandwidth" is not the same thing as
> 2) Further down the data sheet there is a graph which shows the gain at
> 10MHz as 45dB (Gain 1)
> How are these two pieces of data reconciled?
Gain-Bandwidth product, if that was what you thought. It is just the
bandwidth when the gain is set to 1.0.
Bandwidth is 40 MHz (typ) at Gain 1. Gain 1 has a minimum gain of 48
dB (250 V/V).
7507 2012-05-13 22:17:39 victor Re: Unity Gain Bandwidth This amplifier is not an operational amplifier.
An operational amplifier has a dominant pole which means that its open loop gain slope is 20dB/decade in order to preserve stability when it is connected in a circuit with negative feedback.
The NE592 has a gain slope of much higher than 20dB/decade because it is a broadband amplifier that is not intended to work with external feedback, so you can not talk about gain-bandwidth factor in this amplifier.
Victor - 4Z4ME.
7508 2012-05-13 22:27:07 Robert Bennett Re: Unity Gain Bandwidth Many thanks to all who responded.
I see it now.
73 Robert G3WKU
7509 2012-05-14 06:01:48 Andy Re: Unity Gain Bandwidth > The NE592 ... is not intended to work with external feedback, ...Somewhat off-topic reply: I remember an oddball application that used
the uA733 (which is essentially the same as, or a very close cousin to
the NE592) in a circuit with feedback. As I recall, the 733 was
followed by a few transistors, and then a bank of vacuum tubes, with
differential feedback around the whole shebang. It was about as odd
as they come, or at least I thought so at the time. I thought it was
cool that this circuit was a hybrid of all three technologies: tubes,
transistors, and ICs, all within the same feedback amplifier.
I agree that the NE592 isn't meant to be used with external feedback,
and it lacks the controlled response usually necessary to use it with
negative feedback. This other circuit undoubtedly must have tailored
its open-loop response to keep it closed-loop stable.
7510 2012-05-14 06:04:31 Norman Dennett Re: Unity Gain Bandwidth Hi Andy,
Article received as a .pdf no Problem. Thank you.
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