Differential amplifier circuit
View Patent ↗Provided is a differential amplifier circuit in which an offset voltage is independent from input voltages. A first correction current generation circuit and a second correction current generation circuit are provided and configured to cause the same current as a current flowing through a folded cascode amplifying stage to flow into an output stage. Accordingly, transistors included in the folded cascode amplifying stage and transistors included in the output stage have the same bias condition.
1. A differential amplifier circuit, comprising:
a first input stage comprising a pair of PMOS transistors and a first current source, for causing an output current to flow based on two input voltages;
a second input stage comprising a pair of NMOS transistors and a second current source, for causing an output current to flow based on the two input voltages;
a folded cascode amplifying stage, into which the output current of the first input stage flows and from which the output current of the second input stage is drawn, thereby outputting a voltage;
an output stage for outputting an output voltage based on the voltage of the folded cascode amplifying stage;
a first correction current generation circuit for causing a first correction current to flow into the output stage based on a supply current of the first current source; and
a second correction current generation circuit for drawing a second correction current from the output stage based on a supply current of the second current source.
2. A differential amplifier circuit according to claim 1 ,
wherein the first correction current generation circuit comprises:
a third PMOS transistor of the same size as a size of one of the pair of PMOS transistors, the third PMOS transistor including a gate connected to a gate of the one of the pair of PMOS transistors; and
a third current source of half a size of the first current source, the third current source being provided to a source of the third PMOS transistor, and
wherein the second correction current generation circuit comprises:
a third NMOS transistor of the same size as a size of one of the pair of NMOS transistors, the third NMOS transistor including a gate connected to a gate of the one of the pair of NMOS transistors; and
a fourth current source of half a size of the second current source, the fourth current source being provided to a source of the third NMOS transistor.
3. A differential amplifier circuit according to claim 1 , further comprising:
a first clamp circuit provided to one end of a current mirror circuit included in the folded cascode amplifying stage;
a second clamp circuit provided to another end of the current mirror circuit; and
a third clamp circuit provided to an output terminal of the output stage.
4. A differential amplifier circuit according to claim 2 , further comprising:
a first clamp circuit provided to one end of a current mirror circuit included in the folded cascode amplifying stage;
a second clamp circuit provided to another end of the current mirror circuit; and
a third clamp circuit provided to an output terminal of the output stage.