Current Mirror - Practical Approximations

Practical Approximations

For small-signal analysis the current mirror can be approximated by its equivalent Norton impedance .

In large-signal hand analysis, a current mirror is usually and simply approximated by an ideal current source. However, an ideal current source is unrealistic in several respects:

  • it has infinite AC impedance, while a practical mirror has finite impedance
  • it provides the same current regardless of voltage, that is, there are no compliance range requirements
  • it has no frequency limitations, while a real mirror has limitations due to the parasitic capacitances of the transistors
  • the ideal source has no sensitivity to real-world effects like noise, power-supply voltage variations and component tolerances.

Read more about this topic:  Current Mirror

Famous quotes containing the word practical:

    While there are practical and sometimes moral reasons for the decomposition of the family, it coincides neither with what most people in society say they desire nor, especially in the case of children, with their best interests.
    Robert Neelly Bellah (20th century)