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# SN74AHC1GU04: SN74AHC1GU04 Output Problem

Part Number: SN74AHC1GU04
Other Parts Discussed in Thread: AMC1210, SN74LVC1G14, TLV3501

When I used SN74AHC1GU04, I found that the output was different from what I expected. My input is about 2.2V, SN74AHC1GU04 supplies 3.3V, but the output is about 1.7V, is this normal? What is the relationship between the input and output voltage of SN74AHC1GU04? (My understanding is that input = output, in the case of not exceeding VCC. Is this correct?)

• This device is an inverter. When the input voltage is below VIL, then the output is high. When the input voltage is above VIH, then the output is low. In between, the output is undefined.

AHC devices have overvoltage-tolerant inputs; see [FAQ] Can the input voltage (Vi) to my logic device be higher than the supply voltage (Vcc)?

Why are you using an unbuffered ("U") device? Nowadays, the only purpose of such an inverter is to build a Pierce oscillator.

• Hi

I would like to invert my clock,The following illustrates the waveform of the clock

The following is the waveform through the inverter (power supply 3.3V)

The minimum value of the input is 1.3V and the maximum value is 3.6V, but the minimum value of the output is 380mv and the maximum value is 2.42V. Why does this happen. In my understanding, the amplitude should be the same in the opposite direction. Is there any solution? If this inverter is not suitable, is there anything else that can meet my needs?

• This device is not suitable.

Do you want to invert the analog signal, or do you want to get a square wave out of it?

• In fact, I just need to invert the signal, Are there any devices recommended?

Thanks

• Logic devices do not have guaranteed characteristics for analog signals. To invert a sine wave, use a high-speed opamp.

(What do you need the inverted sine wave for?)

• This signal is the CLK signal output from another EVM board（AMC1210) ,I want to input it into the ADC reversely,What should i do？

• But for a clock signal, you do not need a sine wave.

What are the electrical characteristics you need for the inverted clock signal? (And why do you need it inverted?)

• I am also confused, but the CLK output by the output EVM is a sine wave.

Since ADC sampling is triggered by falling edge and opposite to EVM, I hope to make ADC sampling correctly by reversing CLK.（TIer recommended me to do this）

Do you have any suggestion？

• Hey ZZZT,

I think the SN74LVC1G14 would be more suitable here, but you will need to get the input signal to go closer to GND.

• If there is no logic device that can handle input signals in the 1.3 V … 3.6 V range, you can use any high-speed comparator, e.g., TLV3501.