By reference to an amplifier, explain what is meant by negative feedback.
An amplifier circuit incorporating an ideal operational amplifier (op-amp) is shown in the figure below.
The supply for the op-amp is 
. The amplifier circuit is to have a gain of 25. Calculate the resistance of resistor R.
State the value of the output voltage 
of the amplifier in (b) for input voltages 
of
to the inverting input.
.
.
.
