Analog Circuit Design Laboratory Report - MyWeb at WIT ...

ended output voltage Vo is equal the product of the open-loop gain and the differential
voltage, Ed, between pins 2 and 3. The differential voltage, Ed, is equal to the positive
input voltage minus the negative input voltage and it controls the polarity of the output
VO. When Ed is positive VO is positive, and when Ed is negative VO is negative.
V = A E
Eq. (3)
O
OL
5
d
Ed = V ( + ) ⊥ −V
( −)
⊥
Eq. (4)
One function of the op-amp is as a voltage comparator, see Figure 2.
When an AC voltage source, Ei, is connected to the positive input, pin 3, the op-amp is
working as a non-inverting voltage comparator. If the negative input, pin 2, is connected
directly to ground, the reference voltage Vref is equal to 0V.
Figure 2- Voltage Comparator
As Ei crosses Vref, going from positive to negative, the polarity of VO reverses and
VO changes from +Vsat to –Vsat. When Ei again crosses Vref, negative to positive, VO goes
from –Vsat to +Vsat. When the voltage source is connected to the negative input, pin 2,