Schmitt trigger

Abstract

The invention discloses a Schmitt trigger. The Schmitt trigger comprises a first transistor to a sixth transistor, an input end, and an output end, and further comprises a seventh transistor; the seventh transistor is connected between a fifth transistor and a first node in series or connected between the sixth transistor and a second node in series; the grid of the seventh transistor is connected with the output end, and the source electrode of the seventh transistor is connected with the drain electrode. The seventh transistor is used as a positive feedback capacitor in the Schmitt trigger, the output end voltage is boosted along the boosting of the first node voltage through the capacitive coupling under the high frequency, so that the second transistor can be earlier switched on, and an output end signal can be faster overturned. Or, the output end voltage is faster dropped along the dropping of the second node voltage through the capacitive coupling under the high frequency, so that the third transistor can be earlier switched on, and the output end signal can be faster overturned. Aiming at a Schmitt trigger circuit composed of high-threshold voltage devices, the voltage output character is improved when the Schmitt trigger is located at the low first potential end and the input end signal is out of full amplitude.

Description

technical field [0001] The invention relates to the technical field of semiconductor integrated circuit design, in particular to a Schmitt trigger with positive feedback under low voltage application. Background technique [0002] The Schmitt trigger is an inverter with hysteresis characteristics, and it will be used as an anti-noise shaping circuit in digital circuits. Circuit structure reference of Schmitt trigger figure 1 As shown, it includes transistors M1, M2, M3, M4, M5 and M6. When the input terminal IN is at low level, transistors M1 and M2 are turned on, M3, M4, M5 and M6 are turned off, and the output terminal OUT outputs high level. When the input terminal IN is at a high level, the transistors M1, M2, M5 and M6 are turned off, M3 and M4 are turned on, and the output terminal OUT outputs a low level. Moreover, when the input terminal IN gradually rises from low level to high level, when the voltage rises to the threshold voltage of M4, M4 is turned on. Since th...

AI Technical Summary

Problems solved by technology

[0004] The purpose of the present invention is to provide a Schmitt trigger circuit with positive feedback for a Schmitt trigger circuit composed of high threshold voltage devices, which solves the problem of output voltage reversal delay under low power supply voltage and when the input signal is not full. problem, thereby improving the output characteristics of the Schmitt trigger

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