Low frequency analysis disregarding channel length modulation

  In this Section, the current mirror is analysed under the assumption , i.e. disregarding channel length modulation. The input current is assumed to be positive, such that the input transistor M₁ operates in saturation. The following expression holds:

Note that V_T>0 for N-channel enhancement transistors. Now, we can calculate V_GS1 from Equation (3.2):

For the output transistor M₂ we get:

Thus, M₂ operates in saturation when
 
The current in the output transistor M₂ under normal conditions (i.e.\ M₂ operates in saturation) is calculated using Equation (3.2):

Thus, under the given conditions, the current mirror works ideally, and the current transfer factor is
 
Note that B₀ is independent of the process parameters V_T and , as long as the parameters are identical for both transistors. In Section 4.5, the consequences of minor relative variations will be analysed.