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Original question:

Switch selection for +/- 8V square wave with 20kHz frequency

CD74HTC4051

user5994204
Prodigy 185 points
Other Parts Discussed in Thread: OPA656, LMH6559

Hello everyone,I ues 74HCT4051 as Multiplex analog switch,I have followed the circuit structure you recommended, but the output voltage is still not ideal.I hope you can give me some Suggestions to solve this problem,thank you very much.

The circuit structure diagram and DC simulation results are shown below:

Fig 1 1MΩ connect to the Ground.

                                           Input resister value of R5

                                Fig 2 DC simulation result of fig1

Fig 3 Directly connect to the Ground.

  Fig 4 DC simulation result of fig3

  • 0
    TI__Genius 9132 points

    Hi,

    In the schematic, can you highlight where you are using the TI switch? Looks like you are using an ideal switch where there is no voltage drop across the switch. If your AM1 voltage is "5 V", you will get the same voltage at VM1 for an ideal switch.

    Most likely the drop in the output voltage would be affected by the opamp (OPA656) - I have passed this to the opamp team to get their input.

  • 0 in reply to Saminah C
    TI__Genius 14136 points

    What is not ideal? You are changing the gain. Even with the LMH6559 grounded, it will produce an offset.