Integrated IGFET constant current source

Claim 1

A monolithically integrated circuit for an IGFET-constant current source containing a source-drain series arrangement of two IGFET's of one conductivity type in series between the voltage supply and the substrate, in which series arrangement the gate electrode of the first load IGFET of the series arrangement, as applied to the first pole of the voltage supply, is connected to the first pole of the voltage supply, and the common connection point of the two IGFET's is connected to the gate electrode of a current-source IGFET whose source electrode is applied to the substrate, wherein the improvement comprises that: when using enhancement IGFET's of the same channel conductivity type, the gate electrode of the second IGFET (T 2 ) of the series arrangement is connected to the common connection point (1) of a further source-drain series arrangement of two IGFET's (TL 1 , T 1 ) arranged in series between the first pole and the substrate, that in the further source-drain series arrangement, the gate electrode of the load-IGFET (T L1 ) as applied to the first pole of the supply voltage (U DD ) is applied to this first pole of the voltage supply (U DD ), and that the gate electrode of the second IGFET (T 1 ) is applied to the common connection point (1) thereof, and that the condition (β 1 /β L1 )=1 is extensively approximated and that the condition 4<β 2 /β L2 ≦9 is satisfied. wherein β 1 indicates the mutual conductance constant of the second IGFET (T 1 ) of said further series arrangement, wherein β L1 indicates the mutual conductance constant of the load-IGFET of said further series arrangement, wherein β 2 indicates the mutual conductance constant of the second IGFET (T 2 ) of the series arrangement, and wherein β L2 indicates the mutual conductance constant of the load-IGFET of the series arrangement.