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I am trying to make use the CD4081B AND logic gate for starting basic Logic Gate circuits and I am trying to find the input current at 5 volts for the chip. I was wondering how to find it in the datasheet because I cannot. If anyone could help find it or show me how to calculate it myself that would be great.

Here is the link to the CD4081B datasheet: http://www.ti.com/lit/ds/symlink/cd4081b.pdf

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If you mean the current drawn by the chip in quiescent / static conditions then it is given in an alternative datasheet by Fairchild.

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Figure 1. Quiescent device current is very low. (1) The device current. (2) The input current.

Generally the input resistance is so high that we ignore it. The situation changes when we feed it with a high frequency signal. The input capacitance can become a significant factor as it has to be charged and discharged.

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Figure 2. (3) Input capacitance.

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  • $\begingroup$ Does that mean that I can supply 5 volts and 1 Amp DC to the input of the chip and it will not harm the IC chip since the input resistance is so high? $\endgroup$ – Andrew Mar 5 '18 at 19:50
  • $\begingroup$ What do you mean by "input"? The power pin or an input pin? Let me get you thinking: if I connect a 20 W light bulb to the 5 GW Irish national grid how much power do you think it will consume? (Hint: my house hasn't exploded in a fireball.) Now, if I connect a logic input pin that draws 0.3 µA to a 1 A supply how much current do you think it will draw? By the way, there's an Electrical Engineering stack which is a better place for this type of question. Word your questions well though. We get a lot of bad questions that get closed. $\endgroup$ – Transistor Mar 5 '18 at 21:02
  • $\begingroup$ Pin 14 on the CD4071B for the IC’s power which I believe is Vdd if I’m reading that right. So the supply voltage/current for pin 14. $\endgroup$ – Andrew Mar 6 '18 at 15:01
  • $\begingroup$ Then it's $ I_{dd} $ as shown in (1). $\endgroup$ – Transistor Mar 6 '18 at 15:24

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