Constant current circuit for supplying a constant current to operating circuits
View Patent ↗In order to prevent interference of signals in a plurality of outputs from a current mirror circuit, the current mirror circuit comprises a current mirror input transistor Q 1 through which a constant current flows and a plurality of current mirror output transistors Q 7 and Q 8 which have control ends commonly connected to a control end of the current mirror input transistor Q 1 . The constant current is supplied from the plurality of current mirror output transistors Q 7 and Q 8 to a plurality of operating circuits. Further, at least one of the plurality of current mirror output transistors Q 7 and Q 8 is equipped with a low pass filter for removing a high-frequency component contained in a current output from the at least one of the plurality of current mirror output transistors Q 7 and Q 8.
1. A constant current circuit for supplying a constant current to each of a plurality of operating circuits, comprising:
a current mirror input transistor through which an input-side constant current flows; and
a plurality of current mirror output transistors that each have a control end that is commonly connected to a control end of the current mirror input transistor, and each of the plurality of current mirror output transistors supply an output-side constant current to a corresponding one of the plurality of operating circuits,
wherein the output-side constant current corresponds in magnitude to the input-side constant current,
wherein at least one of the plurality of current mirror output transistors is equipped with a low pass filter for removing a high-frequency component contained in the respective output-side constant current,
wherein the low pass filter comprises two resistors and a capacitor,
wherein the two resistors are connected in series at a common node, one of the two resistors connected in series is connected to a collector node of at least one of the plurality of current mirror output transistors, one end of the capacitor is connected to the common node, and one end of the capacitor is connected to a ground node, and
wherein the low pass filter removes the high-frequency component in the output-side current.
2. The constant current circuit according to claim 1 , wherein the low pass filter for removing the high-frequency component is connected to an output side of the current mirror output transistors.
3. The constant current circuit according to claim 2 , wherein the low pass filter for removing the high-frequency component is connected to the output side of each of the plurality of current mirror output transistors.
4. The constant current circuit according to claim 1 , wherein the low pass filter is configured using a resistance and a parasitic capacitance which is parasitic on both the resistance and a line connected to the resistance.
5. The constant current circuit according to claim 1 , wherein the constant current circuit is integrated into one cell, and
output currents from the plurality of current mirror output transistors are respectively output from a plurality of output terminals of the one cell.