Improved voltage comparator

Abstract

The invention provides a voltage comparator. The voltage comparator comprises a band-gap reference voltage power circuit and a comparison unit, wherein the band-gap reference voltage power circuit provides band-gap reference voltage; the first input end of the comparison unit receives the band-gap reference voltage, the second input end of the comparison unit is connected with target voltage, andthe output end of the comparison unit outputs a comparison result. The band-gap reference voltage power circuit comprises an operational amplifier, a third resistor, a first intermediate node, a second intermediate node, a sampling switch, a first capacitor, a filter, a reference voltage output end, a switch combination circuit, N bipolar transistors and a control circuit. In different time periods, the switch combination circuit enables the N bipolar transistors to be connected to the second intermediate node one by one, and the remaining bipolar transistors are connected to the first intermediate node in parallel; through rotation, mismatch between the bipolar transistors can be averaged, then higher output voltage precision can be realized, and the voltage comparator can output a more accurate comparison result.

Description

【Technical field】 [0001] The invention relates to the technical field of electronic circuits, in particular to an improved voltage comparator. 【Background technique】 [0002] Bandgap reference voltage sources are widely used in various analog circuits. In practical applications, high-precision bandgap reference voltage sources are favored. Please refer to figure 1 As shown, it is a schematic circuit diagram of a bandgap reference voltage source in the prior art, which includes resistors R1, R2, R3, bipolar transistors PNP transistors Q1, Q2, and an operational amplifier OP. Generally, the emitter area of ​​Q1 is designed to be larger than that of Q2, for example, its ratio is K:1. In order to achieve a better matching effect in actual design, Q1 is generally designed as K PNP transistors in parallel with Q2. In one example K=4. Generally, the resistance values ​​of resistors R1 and R2 are designed to be the same, and are designed to be M times the resistance value of R3,...

AI Technical Summary

Problems solved by technology

[0003] Although Q1 is designed as K transistors in parallel with Q2, there is a mismatch between each transistor in Q1 and Q2, that is, when mass production, there will be differences between chips, and these differences will cause inaccurate VBG, And this difference will vary due to package stress effects

Even at the wafer or chip stage, VBG is adjusted accurately through trimming technology, but after packaging, due to the influence of packaging stress, there are deviations between chips

[0004] Therefore, due to the deviation of the generated bandgap reference voltage VGB, the output result of the voltage comparator using such a bandgap reference voltage source is also inaccurate.

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