Current signal conditioning circuit

叶景富

Current signal conditioning circuit [Copy link]

Please teach me the working principle, the role of the op amp, and the circuit design intention

maychang

U11A is a current-voltage converter, and its input Ig1 is a current signal. U11B constitutes a second-order low-pass filter.

maychang

【Circuit design intention】

You should ask the original designer of the circuit, as outsiders cannot see the design intent.

叶景富

maychang published on 2023-7-11 17:12 U11A is a current-voltage converter, and its input Ig1 is a current signal. U11B constitutes a second-order low-pass filter.

What is the function of the capacitor in parallel with the feedback loop of U11A? If it is filtering, can the cutoff frequency be calculated?

maychang

Ye Jingfu posted on 2023-7-11 17:33 What is the function of the capacitor in parallel with the feedback loop of U11A? If it is filtering, can the cutoff frequency be calculated?

What is the function of the capacitor in parallel with the U11A feedback loop?

The capacitor connected in parallel reduces the resistance of the transimpedance amplifier at high frequencies, which can be regarded as reducing the sensitivity of the current-voltage conversion at high frequencies.

maychang

Ye Jingfu posted on 2023-7-11 17:33 What is the function of the capacitor in parallel with the feedback loop of U11A? If it is filtering, can the cutoff frequency be calculated?

[If it is filtering, can the cutoff frequency be calculated?]

This capacitor is not generally called a filter, but it does have similarities to a first-order low-pass filter and can be said to be a filter.

The cut-off frequency (corner frequency) is the resistance value of R106 and R112 in parallel, multiplied by the capacitance of C149. In the figure, R106 is much larger than R112, so the corner frequency is approximately R112 multiplied by C149.