Marking and Identification of SMD/chip diodes
1. SMD diode model marking and polarity identification
The model of SMD diode is marked with letters, numerical codes or letter + numerical code marking method and color (code) marking method.
For example, the electrical parameters of the printed word "A3" are as follows: PD=0.15W; IF=0.1A; VB=80V; Trr=4ns. In the color labeling method, the model is mainly found by the color marked on the negative side, and then the parameter value is found by the model.
SMD diode polarity identification method: glass tubular SMD diode, the red end is the positive electrode, the black end is the negative electrode; the rectangular SMD diode, the one end with the white horizontal line is the negative electrode.
2. SMD diode quality measurement
A normal SMD diode, measured on the circuit, has a small forward resistance and a large reverse resistance, and there is a significant difference in resistance between the two. Disconnect the circuit, if measured with a pointer multimeter, the forward resistance is about 3kΩ, and the reverse resistance is hundreds of kiloohms or infinity; The voltage drop is infinite.
3. SMD diode identification on board
On the circuit board, the component number of SMD diode generally starts with the letter D, such as D1, D2, etc., or VD, such as VD1, VD2, etc.; or DD, such as DD1, DD2, etc.
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