Low pass filter circuit and voltage regulator

摘要

Provided are a low pass filter circuit having a small output voltage shift caused by a substrate leakage current at high temperature, and a voltage regulator using the low pass filter circuit, which has a small output voltage shift at high temperature. In a low pass filter circuit using a PMOS transistor as a resistive element, a back gate terminal of the PMOS transistor is set to have a higher voltage than a source of the PMOS transistor. Further, in a voltage regulator incorporating the low pass filter circuit to an output of a reference voltage circuit, the voltage of the back gate terminal of the PMOS transistor which is higher than that of the source thereof is generated by the reference voltage circuit.

主权项

1. A low pass filter circuit comprising:
a first PMOS transistor; a second PMOS transistor; a capacitor; a back gate voltage source connected between a back gate terminal and an input terminal of the low pass filter circuit; and a current source, the first PMOS transistor including a source connected to the input terminal, a drain connected to an output terminal of the low pass filter circuit, and a gate connected to one terminal of the current source, the second PMOS transistor including a source connected to the input terminal, and a gate and a drain connected to the one terminal of the current source, the capacitor being connected between the output terminal and a ground terminal, the current source having another terminal grounded, the first PMOS transistor and the second PMOS transistor connected to the back gate terminal and having the same substrate potential which is higher than a source potential of the first PMOS transistor and the second PMOS transistor, wherein a voltage at the back gate terminal is higher than that of the ground terminal by a predetermined amount.