Circuit for compensation of leakage current-induced offset in a single-ended op-amp
An electronic device includes an operational amplifier, with the operational amplifier having an amplifier input stage coupled with a first output node to an amplifier output stage. A compensation capacitance is connected between an output node of the amplifier output stage and the first output node of the amplifier input stage, thereby operating as a compensator for stabilizing the operational amplifier. The compensation capacitance provides a parasitic diode drawing a first leakage current from the first output node of the amplifier input stage, a leakage current compensation circuit being coupled to the first output node of the amplifier input stage and coupled to a second output node of the amplifier input stage for drawing a first current from the first output node and a second current from the second output node. The leakage current compensation circuit is adapted such that the second current is greater than the first current by an amount corresponding to the first leakage current.
1. An electronic device including an operational amplifier, the operational amplifier comprising:
an amplifier input stage coupled with a first output node (V 1 ) to an amplifier output stage;
a compensation capacitance (CM) connected between an output node (Vout) of the amplifier output stage and the first output node (V 1 ) of the amplifier input stage thereby operating as a compensator for stabilizing the operational amplifier, the compensation capacitance (CM) providing a parasitic diode (D) drawing a first leakage current (Ileak 1 ) from the first output node (V 1 ) of the amplifier input stage;
a leakage current compensation circuit (M 6 , M 7 , M 8 , M 9 , I 2 , I 2 ′) being coupled to the first output node (V 1 ) of the amplifier input stage and coupled to a second output node (V 3 ) of the amplifier input stage for drawing a first current (I 5 ) from the first output node (V 1 ) and a second current (I 3 ) from the second output node (V 3 ), wherein the leakage current compensation circuit is adapted such that the second current (I 3 ) is greater than the first current (I 5 ) by an amount corresponding to the first leakage current (Ileak 1 ).
2. An electronic device including an operational amplifier, the operational amplifier comprising:
an amplifier input stage coupled with a first output node (V 1 ) to an amplifier output stage;
a compensation capacitance (CM) connected between an output node (Vout) of the amplifier output stage and the first output node (V 1 ) of the amplifier input stage thereby operating as a compensator for stabilizing the operational amplifier, the compensation capacitance (CM) providing a parasitic diode (D) drawing a first leakage current (Ileak 1 ) from the first output node (V 1 ) of the amplifier input stage;
a leakage current compensation circuit (M 6 , M 7 , M 8 , M 9 , I 2 , I 2 ′) being coupled to the first output node (V 1 ) of the amplifier input stage and coupled to a second output node (V 3 ) of the amplifier input stage for drawing a first current (I 5 ) from the first output node (V 1 ) and a second current (I 3 ) from the second output node (V 3 ), wherein the leakage current compensation circuit is adapted such that the second current (I 3 ) is greater than the first current (I 5 ) by an amount corresponding to the first leakage current (Ileak 1 ),
wherein the leakage current compensation circuit comprises a diode element (D 2 ) having a second leakage current (Ileak 2 ) which is a factor k smaller than the first leakage current (Ileak 1 ) and a first current mirror (M 6 , M 7 ) for amplifying the second leakage (Ileak 2 ) current by a factor k.
3. The electronic device according to claim 1 , wherein the compensation capacitance (CM) comprises two capacitors (C 1 , C 2 ) coupled in an anti-parallel arrangement for compensating a nonlinearity of a single capacitor (C 1 , C 2 ).
4. The electronic device according to claim 2 , wherein the compensation capacitance (CM) comprises two capacitors (C 1 , C 2 ) coupled in an anti-parallel arrangement for compensating a nonlinearity of a single capacitor (C 1 , C 2 ).
5. The electronic device according to claim 2 , wherein the first current mirror (M 6 , M 7 ) having a factor k is coupled to the first output node (V 1 ) of the amplifier input stage and the leakage current compensation circuit further comprises a second current mirror (M 8 , M 9 ) having a factor k coupled to the second output node (V 3 ) of the amplifier input stage, and wherein the diode element (D 2 ) is coupled to the first current mirror (M 6 , M 7 ) so as to reduce the first current (I 5 ) by an amount corresponding to the first leakage current (Ileak 1 ).
6. An electronic device including an operational amplifier, the operational amplifier comprising:
an amplifier input stage coupled with a first output node (V 1 ) to an amplifier output stage;
a compensation capacitance (CM) connected between an output node (Vout) of the amplifier output stage and the first output node (V 1 ) of the amplifier input stage thereby operating as a compensator for stabilizing the operational amplifier, the compensation capacitance (CM) providing a parasitic diode (D) drawing a first leakage current (Ileak 1 ) from the first output node (V 1 ) of the amplifier input stage;
a leakage current compensation circuit (M 6 , M 7 , M 8 , M 9 , I 2 , I 2 ′) being coupled to the first output node (V 1 ) of the amplifier input stage and coupled to a second output node (V 3 ) of the amplifier input stage for drawing a first current (I 5 ) from the first output node (V 1 ) and a second current (I 3 ) from the second output node (V 3 ), wherein the leakage current compensation circuit is adapted such that the second current (I 3 ) is greater than the first current (I 5 ) by an amount corresponding to the first leakage current (Ileak 1 ), wherein the compensation capacitance (CM) comprises two capacitors (C 1 , C 2 ) coupled in an anti-parallel arrangement for compensating a nonlinearity of a single capacitor (C 1 , C 2 ), and
wherein a first current mirror (M 6 , M 7 ) having a factor k is coupled to the first output node (V 1 ) of the amplifier input stage and the leakage current compensation circuit further comprises a second current mirror (M 8 , M 9 ) having a factor k coupled to the second output node (V 3 ) of the amplifier input stage, and wherein the diode element (D 2 ) is coupled to the first current mirror (M 6 , M 7 ) so as to reduce the first current (I 5 ) by an amount corresponding to the first leakage current (Ileak 1 ).
7. The electronic device according to claim 4 , wherein the first current mirror (M 6 , M 7 ) having a factor k is coupled to the first output node (V 1 ) of the amplifier input stage and the leakage current compensation circuit further comprises a second current mirror (M 8 , M 9 ) having a factor k coupled to the second output node (V 3 ) of the amplifier input stage, and wherein the diode element (D 2 ) is coupled to the first current mirror (M 6 , M 7 ) so as to reduce the first current (I 5 ) by an amount corresponding to the first leakage current (Ileak 1 ).