Patent ID: 6885239

Claim:
A mobility proportion current generator which generates a current proportional to mobility, comprising: a voltage adder including a first MOS transistor having the mobility, the voltage adder adding a voltage, whose temperature dependency is small with respect to the mobility, and a threshold voltage of the first MOS transistor to output a sum voltage; and a second MOS transistor including a source terminal, a gate terminal and a drain terminal, the sum voltage of the voltage adder being applied between the gate terminal and the source terminal of the second MOS transistor to output a current proportional to the mobility from the drain terminal of the second MOS transistor, the voltage adder comprising a first current source that outputs a first current whose temperature dependency is small with respect to the mobility, a first resistor producing a voltage whose temperature dependency is small with respect to the mobility when the first current flows through the first resistor, and a second current source which is connected to the first MOS transistor and outputs a second current whose temperature dependency is small with respect to the mobility and which is smaller than the first current, the first MOS transistor generating the sum voltage by adding a gate-source voltage of the first MOS transistor and the voltage produced by the first resistor at the source terminal of the first MOS transistor.