Explain the concept of bandwidth with regard to a real op-amp and how this differs from the ideal op-amp.
Ideal op-amps are considered to have infinite open loop gain at any frequency, meaning that in a feedback circuit the output voltage will always be as large as it needs to be to bring the potential difference between the inputs to zero. In practice an amplifier has a large but finite open-loop gain and experiences a rapid falloff in output voltage beyond a cutoff frequency, acting effectively as a low-pass filter. The cutoff frequency varies with closed-loop amplifier circuits implimenting feedback, with lower gains giving a greater bandwidth, this can be expressed via the Gain-Bandwidth Product where Gain*BW is constant for a given op-amp, this can be visualised with a log/log plot of gain/frequency.Another factor influencing the bandwidth of a real op-amp is the slew rate, the maximum rate of change of the ouput voltage (V per ms), ideal op-amps are considered to have infinite maximum slew rate and therefore will always match the waveform of the input differential. In a real op-amp the slew rate limit causes distortions of the output signal where the input rate of change exceeds the component's maximum, this may be steady state (where the input frequency is constant but above the limit) or transient (where parts of a wave, such as in a square or sawtooth function, have high rates of change), as with the first example this may be mitigated by reducing the gain via a feedback loop so that the voltage change required by Vout is within the component limits.
