Do you know some precautions when designing pseudo circuits?

Everyone knows about analog circuits, so what are the precautions? Is analog circuits easy to learn? Some people say: It is easy to learn, but the design of analog circuits is quite difficult. Many engineers have said: The design of analog circuits is the most troublesome. It is also the most deadly part of design! Today, the editor has helped electronic engineers summarize 12 issues that should be paid attention to in analog circuit design. Follow the editor and take a look!

1) In order to obtain a feedback circuit with good stability, it is usually required to use a small resistor or choke outside the feedback loop to provide a buffer for the capacitive load.

2) The integral feedback circuit usually requires a small resistor (about 560 ohms) in series with each integral capacitor greater than 10pF.

3) Do not use active circuits for filtering or controlling the RF bandwidth of EMC outside the feedback loop, but only use passive components (preferably RC circuits). The integral feedback method is effective only at frequencies where the op amp's open-loop gain is greater than the closed-loop gain. At higher frequencies, the integrating circuit cannot control the frequency response.

4) In order to obtain a stable linear circuit, all connections must be protected using passive filters or other suppression methods (such as optical isolation).

5) Use EMC filters, and the filters related to the IC should be connected to the local 0V reference plane.

6) Input and output filters should be placed at the connections of external cables. Any wire connections inside the unshielded system need to be filtered because of the antenna effect. In addition, filtering is also required at the conductor connections inside shielded systems of converters with digital signal processing or switching mode.

7) High-quality RF decoupling is required at the power and ground reference pins of analog ICs, just as with digital ICs. But analog ICs usually require low-frequency power supply decoupling because the power supply noise rejection ratio (PSRR) of analog components increases very little above 1KHz. RC or LC filtering should be used on the analog power traces of every op amp, comparator, and data converter. The power filter's corner frequency should compensate for the device's PSRR corner frequency and slope to achieve the desired PSRR over the entire operating frequency range.

8) For high-speed analog signals, transmission line technology is necessary depending on its connection length and the highest frequency of communication. Even for low-frequency signals, the use of transmission line technology can improve their immunity to interference, but transmission lines that are not properly matched will create antenna effects.

9) Avoid using high-impedance inputs or outputs, which are very sensitive to electric fields.

10) Since most of the radiation is generated by common-mode voltage and current, and because most of the environmental electromagnetic interference is caused by common-mode problems, the use of balanced transmitting and receiving (differential mode) technology in analog circuits will It has good EMC effect and can reduce crosstalk. The balanced circuit (differential circuit) driver does not use the 0V reference system as the return current loop, so large current loops can be avoided, thereby reducing RF radiation.

11) The comparator must have hysteresis (positive feedback) to prevent erroneous output conversions due to noise and interference, and to prevent oscillation at the break point. Don't use a faster comparator than needed (keep dV/dt within the required range, as low as possible).

12) Some analog ICs themselves are particularly sensitive to radio frequency fields, so it is often necessary to use a small metal shielding box installed on the PCB and connected to the ground plane of the PCB to shield such analog components. Note that the heat dissipation strip must be ensured. The above are some precautions for analog circuit design. I hope they can help you.