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CD4081BE Troubles

Discussion in 'Microcontrollers, Programming and IoT' started by Buffaloham, Oct 7, 2018.

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  1. Buffaloham


    Oct 7, 2018
    Hello I am not new to electronics but new to ICs and am trying to hook up this CD4081BE (texas instruments) 2 input logic gate to 6 volts and looking at the low-resolution datasheet (Here) is hard to read and does no help and the outputs of the gates always turn a led on no matter what you do

    What I have tried:

    hooking it up the simple way Neg and Pos on pin 1 & 14 which was said the pos and neg was on the datasheet
    pin 8 and 9 where inputs connected to 6V and a led is connected to pin 10 which is connected to ground
    Doesn't work

    hooking buttons with capacitors to its inputs and tried
    Doesn't work

    i didn't similar other ways but they all don't work i sorry if i sound stupid to you for not knowing something like this but i just don't understand how to use it

    Here is the page i got it from

    PS. sorry for the lack of information but there is basically no information i could find about it apart from all of this
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    The 4081 is a CMOS circuit and as such needs to have all its inputs tied to a defined logic level, either high or low. It is nod only bad practice to leave inputs unconnected, it may lead to the destruction of the circuit.
    Therefore connect all inputs to either GND or VCC. You can use a direct connection, but I recommend you use pull-up resistors or pull-down resistors (100 kΩ are fine for this type of chip) to be able to override the static logic level (as defined by the resistors) with another signal (finally you'll want to control the inputs, not have them at static levels).#
    This applies also to all unused gates!

    While some hobbyist applications use the limited current drive capability of the 40xx series chips to directly drive an LED, this is bad practice. Use a current limiting resistor to drive the LED.
  3. Buffaloham


    Oct 7, 2018
    thanks man i try it out

    Wow thanks man it helped A LOT it actually works all I needed was a pull-up resistor and apparently one of the buttons were broken

    am sorry if i don't sound to smart with this its just because am new to ICs but thanks man :D
    Last edited: Oct 8, 2018
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