I am making an experimental circuit and looking at the characteristics.
I have a question, please let me know.
The circuit of several hundred channels is switched by the multiplexer.
The received signal is switched by the following circuit and output to the ADC.
In the noise measurement of the receiving amplifier picked up by the ADC,
In rare cases, channels with a high noise level will occur.
At that time, if the resistor RG is changed, the noise level will change.
This resistance is thought to control ringing due to the multiplexer and the capacitive component of the subsequent stage.
Is there a specific calculation method for the RG value?
Although it is set to 33Ω, this resistance value is changed for channels with a high noise level.
It was confirmed that this reduced the noise level.
I want to know this principle.
The ICs used are ADA4891 and ADG708.
I also investigated the area around the multiplexer,
I think it is due to the characteristics of the amplifier.
Just connect a resistor in series to the output of the amplifier,
No capacitor is attached.
The peripheral circuit is attached.