5u4
Newbie level 3
Hello All!
In the attached EMG amp design the output stage allows for an offset and gain adjustment( for calibration) however there is an interaction between the two adjustments which ultimately prevents the desired output gain. The circuit design includes a preamp stage, 60hz notch filter, RMS to dc converter, and the final amplifier with gain and offset adjustments.
The theory of operation is the inject a 200hz signal (at C61) at two reference levels then adjust the output to to obtain the required levels.
The calibration fails on some hardware, the failure mode is can not obtain sufficient gain.
The question, how can the offset/gain circuit be modified to reduce the interaction between the adjustments such that when the gain is adjusted the offset adjustment does not effect the gain?
In the attached EMG amp design the output stage allows for an offset and gain adjustment( for calibration) however there is an interaction between the two adjustments which ultimately prevents the desired output gain. The circuit design includes a preamp stage, 60hz notch filter, RMS to dc converter, and the final amplifier with gain and offset adjustments.
The theory of operation is the inject a 200hz signal (at C61) at two reference levels then adjust the output to to obtain the required levels.
The calibration fails on some hardware, the failure mode is can not obtain sufficient gain.
The question, how can the offset/gain circuit be modified to reduce the interaction between the adjustments such that when the gain is adjusted the offset adjustment does not effect the gain?