note that although op-amp specifications list an open-loop voltage gain(Avd) the user typically connects the op-amp using feedback resistors to reduce the circuit voltage gain to a much smaller value (closed-loop voltage gain) A number of circuit improvement result from this gain reduction. first, the amplifier voltage gain is a more stable, precise value set by the external resistors, second, the input impedance of the circuit is increased over that of the op-amp alone, third the circuit output impedance is reduced from that of the op-amp alone, and finally, the frequency response of the circuit is increased over that of the op-amp alone
gain-bandwidth
because of the internal compensation circuitry included in an op-amp the voltage gain drops off as frequency increases op-amp specifications provide a description of the gain versus bandwidth. Figure 10.47 provides a plot of gain versus frequency for a typical op-amp. at low frequency down to dc operation the gain is that value listed by the manufacturer's