Constant current source circuit and sampling circuit

Abstract

The invention relates to a constant current source circuit which comprises a main circuit. The main circuit comprises a first three-end stabilizer, a transistor, a sampling resistor and a load, wherein an output end of the first three-end stabilizer is connected with a control electrode of the transistor, a reference electrode of the transistor is connected with a voltage input end, a working electrode is connected with one end of the load, the other end of the load is connected with one end of the sampling resistor, and the other end of the sampling resistor and an input end of the first three-end stabilizer are respectively connected with a reference potential. The constant current source circuit is characterized by further comprising an adjusting unit which comprises a voltage stabilizing unit, a fourth resistor and a fifth resistor. The voltage stabilizing unit generates second reference voltage larger than first reference voltage generated by the first three-end stabilizer and provides the second reference voltage to an adjusting end of the first three-end stabilizer through the fourth resistor, and the fifth resistor is connected between a node between the load and the sampling resistor and the adjusting end of the first three-end stabilizer. The constant current source circuit has the advantages of being high in efficiency, high in current accuracy and good in temperature excursion performance. The invention further relates to a sampling circuit.

Description

technical field [0001] The invention relates to a constant current source circuit and a sampling circuit. Background technique [0002] At present, the constant current source circuit has been widely used in circuits with high requirements for current stability. [0003] In the prior art (see attached figure 1 ) proposed to use a transistor T2 to realize the constant current function. Because the VBE of the transistor T2 is 0.7V, the sampling voltage through the resistor R1 is about 0.6V. The final stable current: I=VBE / R1. The main disadvantage of this circuit is poor current accuracy and high temperature drift. The reason is that the transistor has a large VBE range (0.58-0.75V) and has a high temperature drift. [0004] prior art (see attached figure 2 ) Use a three-terminal shunt regulator U1 to realize the constant current source circuit. Such as figure 2 As shown, the constant current source circuit includes a three-terminal shunt regulator U1 and a transisto...

AI Technical Summary

Problems solved by technology

The main disadvantage of this prior art is that the current sampling voltage is as high as 2.495V resulting in large losses

[0005] In the above two schemes, the voltage across the sampling resistor is close to the forward voltage drop VF (usually 0.7-3.1V) when the light-emitting diode as the load is turned on, so a large power loss is caused

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