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  1. I read an electronic magazine in which there is a report on I can simply describe a level shifter. After reading, I became interested in the circuit of level shifter. So I searched some related materials and information about this topic from google, but it is not specific at all. Today I come to this forum to turn to you to discuss my understandings are appropriate. Here are my personal understandings: Level shifters are mainly composed of an NMOS and two pull-up resistors. Its level shift is two-way. But it needs to meet a few conditions, otherwise it may appear leakage situation. First analyze its working principle. First analysis from left to right function: When the NMOS S-level (source) input is high level 3.3V, NMOS does not turn on, and because its D-class (drain) is pulled up to 5V, so the diode does not turn on. So its output is 5V level. When the NMOS S-pole input is low 0V, then NMOS conduction, then the D-pole output will be pulled to 0V. This results in a conversion from left to right. Reanalyze from right to left: When the NMOS D-stage input is 5V high, due to its S pole through the 4.7k resistor pulled up to 3.3V. So the NMOS and the inside of the diode are not conductive, so the S-level is 3.3V When the N-stage input of the NMOS is a low level of 0V, the level of the S-pole is 0V because the diode inside is turned on. The above analysis assumes that the power is ok. So in practical application should pay attention to: 1, NMOS D-level high level of the plane than the S pole to be high. Otherwise the high level will be through the two-level pull the io level into other levels. 2, NMOS D-level level than the S-level earlier power, otherwise the S-pole will pass through the diode to the D-class leakage. 3, NMOS G level of the best and S-level the same. 4, G level of the electrical plane is greater than the NMOS threshold voltage There is also a relatively simple (with reverse) level shift: The PQ8 pin1 level is 3.3V, but through this circuit, you can change the output level to + VDC (12V). In fact, this circuit can also look at the level shift function is achieved, but this is one-way, and is reverse. It should be noted that the input level must be greater than Vth (MOS threshold voltage). The level to be converted is basically no need to consider. Ps: Excuse me if I was wrong in words or expressions as I am a green hand in the field of level shifters. I need continual learnings. What is your idea ? Do you agree with my ideas ? Any of your ideas would be highly appreciated. May someone would like to help ? thanks in advance
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