Environmental Engineering Reference
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which is always much lower than 1. It is reduced by decreasing the closed-
loop gain and tends to when the amplifiers are used in unity-gain
configuration. This means that for the same amount of power consumption,
the accuracy of a bipolar CFOA is worse than that achieved with a VOA.
However, if we compare the resulting bandwidth of the CFOA and VOA we
get
which shows that the CFOA is superior to the VOA for the same power
consumption by about one order of magnitude. This advantage in terms of
speed is achieved in an open-loop configuration. But to really evaluate the
speed benefit we have to compare the frequency response in a closed-loop
configuration. Since the closed-loop bandwidth is equal to the gain-
bandwidth product of the open-loop gain, we can simply compare the gain-
bandwidth product of the two amplifiers
The above equation reveals that when the amplifiers are used in unity-
gain configuration (with equal to zero), the CFOA gain-bandwidth
product is only twice as great as that of the VOA considered. Moreover, the
bandwidth improvement is not so marked for closed-loop gains greater than
1, since term must be greater than 1 (the CFOA gain-bandwidth is
greater than the VOA's only if condition
is met).
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