Electronic – Bottom half of IC appears not working

digital-logicintegrated-circuitmicrocontrollertransistors

I have a NAND logic gate, the top 6 pins appear to be working fine (4x Input, 2x Output) However the bottom 6 pins on the IC appear not to work.

I was testing the IC via an LED, connecting two high currents to the input and then the output to the LED, it works fine for the top half and not for the bottom.

enter image description here

In relation to the pin map above, I have tried pins KCD, LFE, placing a high current into pins C & D expecting a high input from K and also E & F expecting a high input from L.

Is the IC damaged or am I missing something?

The IC is a Texas Instruments CD4011B

Data Sheet: http://www.ti.com/lit/ds/symlink/cd4011b.pdf

Jacob.

Best Answer

My guess is that the chip has been damaged by electrostatic discharge or by overcurrent.

That CMOS chip's datasheet suggests it's outputs can only handle a few milliamps, not enough to drive a typical 20mA LED directly. Here is an example circuit.

enter image description here

Note that inputs on unused gates are tied to VSS or VDD

Note that a transistor is used to drive the load.

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