CD4051B: output status when no input

George Zhao

Intellectual 1635 points

Part Number: CD4051B

Hi team,

What's the output status of output X, when the input X0 is floating? (X is selected to X0 channel)

Is there any pull-up or pull-down internally on the output stage?

Thanks!

George

over 4 years ago

0 Rami Mooti1 over 4 years ago

TI__Mastermind 35638 points

Hey George,

I believe you're asking about the output when the input is floating (For the CD4051B this would be floating ChannelX and seeing what COM is outputting).
You would simply see what was on the floating input, which would probably just be noise. There aren't any pulldown or pullups internally on this device. It's simply a passive 8:1 device where the signal on the input channel that is selected (determined by the control logic pins A, B & C) will appear on the output.

Thanks!
Rami

0 George Zhao over 4 years ago in reply to Rami Mooti1

TI__Intellectual 1635 points

Hi Rami,

Thanks for prompt reply. Got it.

Do you or team have the circuit structure of the device output stage? As in below functional diagram, the TG block. thanks!

George

+1 Clemens Ladisch over 4 years ago in reply to George Zhao

Guru 317480 points

A transmission gate consists of an N-channel and a P-channel transistor in parallel; see section 2.2 of the application report Selecting the Right Texas Instruments Signal Switch.

+1 Rami Mooti1 over 4 years ago in reply to George Zhao

TI__Mastermind 35638 points

Hey George,

Clemens response is correct. The transmission gate is a parallel NFET and PFET, which allows for a flatter On resistance across voltage inputs.

Thanks,
Rami

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CD4051B: output status when no input