PCB manufacturing and PCB assembly factories
| (1) The integral feedback circuit usually requires a small resistor (about 560Q2) in series, and each integral capacitor is greater than 10PF. |
| (2) In order to obtain a feedback circuit with good stability, it is usually necessary to use a small resistor or choke coil outside the feedback loop to provide a buffer for the capacitive load. |
| (3) In order to obtain a stable linear circuit, all connections must be protected by passive filters or other suppression methods such as opto-isolation. |
| (4) The input and output filters should be placed at the connection of the external cables. Filtering is required at any wiring within an unshielded system due to antenna effects. Additionally, filtering is required at the wiring within shielded systems that use digital signal processing or switch-mode converters. |
| (5) EMC filters should be used, and all IC-related filters should be connected to the local OV reference plane. |
| (6) Outside the feedback loop, do not use active circuits to filter or control the RF bandwidth of EMC, but only use passive components (preferably RC circuits). The integral feedback method is only effective when the open-loop gain of the op amp is greater than the closed-loop gain. At higher frequencies, the integrating circuit cannot control the frequency response. |
| (7) The power and ground reference pins of analo ICs require high-quality RF decoupling, as do digital ICs. However, since the power-to-noise rejection ratio (PSRR) of analo devices barely improves above 1kHz, low-frequency power decoupling is often required in analo chips. The analo power lines for each op amp, comparator, and data converter should be filtered with RC or LC. The corner frequency of the power filter should compensate the PSRR corner frequency and the slope of the device to obtain the desired PSRR over the entire operating frequency range, |
| (8) For high-speed analo signals, transmission line technology is required according to the connection length and the highest frequency of communication. Even for low frequency signals, the use of transmission line techniques can improve their immunity to interference, but without properly matched transmission lines, antenna effects can occur. |
| (9) Avoid using high-impedance inputs or outputs that are very sensitive to electric fields. |
| (10) Since most of the radiation is generated by common-mode voltage and current, and most of the electromagnetic interference in the environment is caused by common-mode problems, using balanced transceiver (differential mode) technology in analo circuits will have a good effect EMC effect, reduce crosstalk. (Differential circuit) The driver does not use the OV reference system as a return loop, so it can avoid high current loops, thereby reducing radiation radiation. |
| (11) The comparator must have a hysteresis (positive feedback) to prevent erroneous output transitions due to noise and interference, and to prevent oscillations at breakpoints. Don't use comparators faster than necessary (keep dV/dt as low as you want). |
| (12) Some analo circuits themselves are particularly sensitive to radio frequency fields, so it is usually necessary to install a small metal shielding box on the PCB and connect to the ground plane of the PCB to shield these analo components. |
