Why folded cascode is very popular building block in CMOS amplifier? Explain its advantages over double cascode.
1 Answer


  1. Easy to stabilize.

  2. Output swing is much better than telescopic and slightly worse than common source output stage

  3. Input common mode is at least as good as two stage amplifier. There is a modified topology where input common mode can go close to rails on both sides.

  4. Input referred noise and offset is worst among the three.

  5. Static power consumption is worse than telescopic.

  6. Higher gain bandwidth for the same current as a two stage miller.

  7. Higher output impedence and therefore dc gain.

  8. Easier to stabilize, since a single high impedence node at output.

  9. Larger input common mode range than a standard differential stage.

As far as output swing, that really depends on your output stage. The swing is still limited by the saturation voltage of the current source and mirror transistors. You will need a class AB output stage if you want to go rail to rail.

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