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MOS current mirrors

 

One of the most important analog building blocks is the current mirror. The basic topology of the current mirror is shown in Figure 4.1. The basic function of a current mirror is to generate an output current IOUT proportional to the input current IIN independent of the voltage VOUT over the output.

  figure910
Figure 4.1: Simple N-channel MOS current mirror.

Intuitively, the input current IIN causes the voltage VIN over the diode coupled input transistor M1. The voltage is applied over the gate-source of the output transistor M2, which in turn generates the output current IOUT. As illustrated in Figure 4.1, the addition of extra outputs is simple: Just add an extra output transistor controlled by the same gate voltage, VIN.





Flemming Stassen (Lektor)
Wed Jan 21 13:35:14 MET 1998