Should the analog switch connection be before or after?

[bunalmis]

The signal around 30mV will be amplified by x100 and then chopped with the analog switch.

If we want to choose between putting the analog switch in front of the amplifier or at the amplifier output, where should we put it and why?

 

[KlausST]

Hi,

would you mind to show a schematic? .. to discuss about.

Klaus

 

[bunalmis]

I haven't tried it yet, but I think option (b) will cause problems due to the x100 gain.

 

[KlausST]

Hi,

None of the pictures show a schematic. Maybe a principle.

In both principles the voltage of the switch output node when OPEN is undefined. What do you achieve with this?

Klaus

 

[danadakk]

https://www.analog.com/media/en/training-seminars/tutorials/MT-088.pdf

I would agree output side in general, but actual application considerations should be
looked at, distortion, noise, chg injection effects....


Regards, Dana.

 

[bunalmis]

 

[KlausST]

Hi ..

without more details from your side ... I have to answer: it depends...

I asked for a schematic, I asked what you want to achieve.

Good luck with your project.


Klaus

 

[bunalmis]

Friends, as can be seen from the circuit drawing, it is a sample hold circuit. The 30mV signal is generated by a low impedance sensor.
x100 standard opamp amplifier.

Since I have not yet designed the complete system, I cannot add the schematic to the forum.

My current problem is whether the sample and hold circuit that I will make with the analog switch should be at the input or at the output.Under normal conditions, I connect the sample hold circuit to the output of the x100 amplifier. But I have never connected it to an input until today and I am wondering if this will cause a problem.

 

[danadakk]

How many channels do you need of the S/H ? What is signal BW you are sampling ?
And of course accuracy, droop specs, etc....


Regards, Dana.

 

[crutschow]

The signal around 30mV will be amplified by x100 and then chopped with the analog switch.

If we want to choose between putting the analog switch in front of the amplifier or at the amplifier output, where should we put it and why?

At the output, since the small amount of switching noise injected into the signal by the switch, will be X100 times less in relation to the signal amplitude.