I just want to add.

The square wave itself is the lowest frequency and the largest of the
sine waves. They seem to decrease in amplitude in some
linear fashion as the harmonics go up.

So like, 0.05 Hz is the fundamental and the harmonics are like
an exact multiple but every other one.
You probably need to see flatly 0.05 to 5Hz
to get a fairly good 20 second square wave
with a 50% duty cycle.
It is my understanding the phase relationship of all such harmonics
must not be altered by the circuitry as the frequency increases.
This means no fancy filtering, just a plain buffer like amplifier.
One which is operating within the gain bandwidth product
which can find within the PDF specification sheets
of the device you are dealing with.
Off The Wall:
I really hate to think uncle sam is keeping such data sheets
on people like manufacturers do on their devices. :-)

Prosit;
geoff




-----Original Message----- 
From: Richard Schneider 
Sent: Monday, December 06, 2010 9:11 PM 
To: psnlist@.............. 
Subject: Re: Testing Amplifier Frequency Response 


Thanks guys, I give each idea some thought.

Rich

On Sun, Dec 5, 2010 at 2:26 PM, Geoffrey  wrote:
Id say generate a square wave to the input.

If you get a square wave out its pretty good response
you need like 100 third order (ODD) harmonica to get a good square wave.
If the top of the wave slopes one way you need better high response.
if it slopes the other you need better low response.

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