Diode has a one-way conductivity, mainly for rectification, regulation and mixing circuits. This paper introduces the parameters and selection principles of rectifier diodes and Zener diodes.

(A) the main parameters of rectifier diodes

1.IF- maximum average rectified current.

Refers to the maximum forward average current allowed by the diode during long term operation. This current is determined by the junction area of the PN junction and the heat dissipation conditions. It should be noted that the average current through the diode can not be greater than this value, and to meet the heat dissipation conditions. For example, 1N4000 series diode IF 1A.

2.VR - maximum reverse operating voltage.

Refers to the maximum reverse voltage at both ends of the diode. If this value is greater than this value, the reverse current (IR) drastically increases, the one-way conductivity of the diode is destroyed, causing reverse breakdown. Usually half of the reverse breakdown voltage (VB) is taken as (VR). For example, VR of 1N4001 is 50V, VR of 1N4007 is 1OOOV.

3.IR-reverse current.

Refers to the reverse current value when the diode is not punctured. The effect of temperature on IR is great. For example, 1N4000 series diodes should be less than 500uA at 100 ° C and IR at 25 ° C should be less than 5uA.

4.VR-breakdown voltage.

Refers to the voltage of the diode's reverse voltammetry characteristic curve. When the reverse is soft, it refers to the voltage at which the reverse leakage current is given.

5.tre - reverse recovery time.

Refers to the reverse recovery time at the specified load, forward current and maximum reverse transient voltage.

6.fm - maximum operating frequency.

Mainly by the PN junction junction capacitance and diffusion capacitance decision, if the operating frequency exceeds fm, the diode's unidirectional conductivity will not be well reflected. For example, 1N4000 series diode fm is 3kHz.

7.CO- zero bias capacitor.

Refers to the sum of the capacity of the diffusion capacitance and the junction capacitance when the voltage across the diode is zero. It is worth noting that, due to the limitations of the manufacturing process, even if the same type of diode its parameters of the dispersion is also great. The parameters given in the manual are often a range. If the test conditions change, the corresponding parameters will also change, for example, at 25 ° C measured 1N5200 series silicon plastic rectifier diodes IR less than 1OuA, and at 100 ° C IR becomes less than 500uA.

(B) the main parameters of the regulator diode

1.Vz-stabilized voltage.

Refers to the regulator voltage through the rated current at both ends of the stable voltage. This value varies slightly depending on the operating current and temperature. Due to differences in the manufacturing process, the same type of regulator voltage regulator is not exactly the same. For example, 2CW51 type regulator Vzmin 3.0V, Vzmax was 3.6V.

2.Iz - Steady current.

Refers to the current value of the tube when the stabilizing tube generates a steady voltage. Below this value, although the regulator can not be regulated, but the regulator will be worse; higher than this value, as long as no more than the rated power loss, is allowed, and the regulator performance will be better, but More power consumption.

3.Rz-dynamic resistance.

Refers to the ratio of the voltage variation at both ends of the regulator to the current. The ratio varies with the operating current, the greater the working current, the smaller the dynamic resistance. For example, when the operating current of the 2CW7C regulator is 5mA, Rz is 18Ω; when the operating current is 1OmA, Rz is 8Ω; when 20mA, Rz is 2Ω;> 20mA is basically this value.

4.Pz-rated power consumption.

Determined by the chip to allow the temperature rise, the value of the stable voltage Vz and allow the maximum current Izm product. For example, 2CW51 regulator Vz is 3V, Izm is 20mA, then the tube Pz is 60mWo 5.Ctv-voltage temperature coefficient. Is to explain the stability of the voltage value by the temperature of the parameters. For example, 2CW58 regulator tube Ctv is +0.07% / ° C, that is, the temperature rise of 1 ° C, the regulator will increase the value of 0.07%. 6. IR - reverse leakage current. Refers to the regulator diode in the specified reverse voltage generated under the leakage current. For example, when VR = 1V for 2CW58 regulator, IR = O.1uA; IR = 10uA at VR = 6V.

(C) the basic principles of selecting diodes

1. Requires a low voltage when the conduction voltage is selected; the reverse current is required to select the silicon tube.

2. Requires a large current when the selected surface type; require high frequency when the election point contact type.

3. Requires reverse breakdown voltage when high silicon tube.

4. Requirements for high temperature when the election silicon tube.