As electronic devices continue to rely on integrated circuits, some important details about individual components, such as the Miller effect, are being forgotten.
John Miller discovered this phenomenon, which sees the input impedance of an inverting amplifier altered by the gain affecting the parasitic capacitance between the input and output terminals of the amplifier.
This effect can be seen inside any inverting amplification device, such as a tube or an op-amp circuit.
While charts suggest that an amplifier with a gain of -60 built around a tube could have an 10 K input impedance supporting 2.5 MHz, the Miller effect reduces this to just 81.5 KHz.
Older op-amps required compensation, but modern devices have compensation capacitors built in.
Some designs may rely on the Miller effect, while others can render the effect irrelevant through the use of a cascade amplifier architecture.
