Often, yes: changing ISO can change analog gain before the ADC, but it depends on the camera and even on the specific ISO setting.

In general, the amount of light captured by the sensor does not change with ISO. What can change is how that sensor signal is amplified and processed during readout.

Possible implementations include:

• on-sensor or readout-stage analog gain, common in many CMOS designs
• a separate analog amplification stage before the ADC
• digital scaling after the ADC
• a mix of analog gain and digital multiplication

So the electrons/ADU relationship may change with ISO on many cameras, but not always. Some cameras may keep the same analog gain over part or all of the ISO range, and some “extended” ISO settings are often achieved digitally rather than with additional analog amplification.

CCD and CMOS designs can also differ: CMOS commonly includes on-chip gain control, while CCD systems typically need amplification off-sensor before conversion.

Bottom line: ISO is not implemented the same way in every camera. Sometimes it changes true pre-ADC gain, sometimes it is partly or entirely digital, and sometimes only certain ISO steps alter analog gain.