In Volume III:
Single-ended and differential amplifiers page:

"It may be helpful to think of a differential amplifier as a variable voltage source controlled by a sensitive voltmeter, as such:"

Do you mean to say:

"It may be helpful to think of a differential amplifier as a variable voltage source controlled by a sensitive potentiometer, as such:"

or:

"It may be helpful to think of a differential amplifier as a variable voltage source controlled by a sensitive power supply, as such:"

 

Actually I think it says what it meant to say, it measures the differential voltage between the inputs, and outputs the voltage difference.

This is not a op amp as such. It is a instrument amplifier.

Show the link where you think the problem is, and we can review the total paragraph.

 

tritch: I believe you are crossing the line between theory and practice. The "variable voltage source controlled by a sensitive voltmeter" intentionally gives no details about how it is made (practice) and is intended to sit inside your brain as a pure supply of voltage (theory).

Using a potentiometer or a power supply to make a voltage source is way too much practical detail. A voltage source here is a purely theoretical entity useful in analysis.

Theory is good, otherwise there is no way to make an analogy explain the amplifier. All you can say is "hey, it works, just keep looking at it until you understand why."


And welcome to the forums.