1445326735900-0

Analogue integrated circuits
circuit of some description — the input voltage (derived
from the wiper of the preset resistor) is applied to the noninverting
input of the op-amp. But in comparison with our
non-inverting amplifier of Figure 9.6, there are no resistors
around the amplifier; instead the output voltage is simply
looped back to the inverting input. So how does it work and
what does it do?
Figure 9.9 A voltage follower circuit: the output is equal to the input. This is
basically a non-inverting circuit
Let’s first consider the non-inverting amplifier gain expression:
and look to see how we can apply it here. Although no resistances
are in this circuit that doesn’t mean that we don’t need
to consider them! Resistor R1 in the circuit of Figure 9.5 can
be seen to be between pin 6 of the op-amp (the output) and
pin 2 (the inverting input). In the circuit of Figure 9.9, on the
other hand, there is a direct connection between pin 6 and
pin 2 — in other words we can imagine that resistor R1 of
this circuit is zero.
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