The development of modern integration technologies is normally driven by the needs
of digital CMOS circuit design. As the sizes of integrated devices decrease, so maximum
voltage ratings also rapidly decrease. Although decreased supply voltages do not
restrict the design of digital circuits, it is harder to design high performance analogue
integrated circuits using new processes.
In digital integration technologies, there are fewer integrated devices available for
circuit design. In a worst case situation, this means that only transistors are available
for analogue circuit design. There may occasionally bee capacitances and resistors
but their values may be small and there are significant parasitic components present.
Thus, if we want to utilise the fastest integration technologies available, we are usually
restricted to active components in the design of integrated analogue circuits.
Since the introduction of integrated circuits, the operational amplifier has served
as the basic building block in analogue circuit design. Since then, new integrated
analogue circuit applications have emerged and the performance requirements for analogue
circuits have changed. Voltage-mode operational amplifier circuits have limited
bandwidth at high closed-loop gains due to the constant gain-bandwidth product. Furthermore,
the limited slew-rate of the operational amplifier affects the large-signal,