I'm using a CD4051 to switch between 5 and -12V with one channel,channel A.Whenever i set channel A to 0 the output is supposed to be 5V and whenever its 1 the output is supposed to be -12V but this is not the case,i've followed the datasheet and connected Vee to -12V and Vdd to 5 as it is required to control voltages in these levels but its not working,the output is giving me something between 0 and -2v,any help?

 

Please check the datasheet again. Vdd -Vee should not exceed 15v but in your case it is 5 - (-12) = 17v.
The 4051 is an analog switch with 8 inputs and 1 output (it also works backwards 1 input and 8 outputs). It is usually used to select small signals like the audio outputs from different devices eg dvd, vcr, tuner etc (Y inputs) and connect one of them to an amplifier etc (Z output). The binary data on the three address lines determines which one of the inputs is connected to the output.
I would suggest that you use a comparator like LM393 for your application.

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