Aluminum electrolytic capacitor and tantalum electrolytic capacitor

Circuit design

(1) Aluminum electrolytic capacitors are divided into positive and negative electrodes. Reverse voltage and AC voltage should not be added. Non-polar capacitors should be used where reverse voltage may occur.

(2) For places where fast charging and discharging are required, aluminum electrolytic capacitors should not be used, and specially designed capacitors with longer life should be selected.

(3) Should not use overload voltage

A. The peak voltage after superimposing the DC voltage and the ripple voltage is lower than the rated value.

B. When using two or more electrolytic capacitors in series, consider using balanced resistors so that the voltage across each capacitor is within its rated range.

(4) When designing the circuit board, it should be noted that there should be no lines at the upper end of the capacitor and the explosion-proof valve, and a clearance of more than 2 mm should be left.

(5) Electrolysis is also the main chemical solvent and electrolytic paper are flammable, and the electrolyte is conductive. When the electrolyte comes into contact with the pc board, the wiring on the pc board may be corroded. So that they smoke or catch fire. Therefore there should be no lines under the electrolytic capacitor.

(6) Design the circuit board to the back to confirm that the heating components are not close to the aluminum electrolytic capacitor or electrolytic capacitor.

1 Aluminum electrolytic capacitor and tantalum electrolytic capacitor

The capacity of the aluminum electrolytic capacitor is relatively large, the series resistance is large, the inductance is large, and it is sensitive to temperature. It is suitable for low frequency filtering where the temperature does not change much and the operating frequency is not high (not higher than 25 kHz). Aluminum electrolytic capacitors have polarity and must be properly grounded during installation, otherwise there is a danger of explosion.

Compared with aluminum electrolytic capacitors, tantalum electrolytic capacitors have obvious advantages in series resistance, inductive reactance, and stability to temperature. However, its operating voltage is low.

2 paper capacitors and polyester film capacitors

Its volume is relatively small, the series resistance is small, and the inductive reactance value is large. It is suitable for low-frequency filtering and bypassing where the capacity is not large and the operating frequency is not high (such as below 1MHz). When using a tubular paper capacitor or a polyester film capacitor, the outer casing can be connected to the reference ground so that the outer casing can function as a shield to reduce the influence of electric field coupling.

3 mica and ceramic capacitors

The volume ratio is small, the series resistance is small, the inductance value is small, and the frequency/capacity characteristics are stable. It is suitable for high frequency filtering, bypass, decoupling in applications with small capacitance and high operating frequency (frequency up to 500MHz). However, such capacitors are less susceptible to transient high-voltage pulses, so they cannot be bridged across low-impedance power lines unless specifically designed.

4 polystyrene capacitor

The series resistance is small, the inductance value is small, and the capacitance is stable with respect to time, temperature and voltage. It is suitable for applications requiring high frequency stability and can be used for high frequency filtering, bypassing, and decoupling.

In terms of temperature drift, the monolith is a positive temperature enthalpy +130 or so, and the CBB is a negative temperature coefficient -230. When used in parallel with an appropriate ratio, the temperature drift can be reduced to a small value.

In terms of price, 钽, tantalum capacitor is the most expensive, monolithic, CBB is cheaper, porcelain is the lowest, but there is a kind of high-frequency zero-temperature drift black point porcelain is slightly more expensive. Mica capacitor Q value is higher, the price is also slightly more expensive.