1N4148 Switching Diode: Datasheet, Pinout, Applications, Comparison

The 1N4148 is a small signal Fast Switching Diode for extreme fast switches. Its packages include DO35, LL34, SOD323, and SOT23. Its 100V reverse withstand voltage and 150mA average forward current are very suitable for ordinary rectification in general occasions. The junction capacitance of 4pF and the reverse recovery time of 4nS are sufficient for most occasions. It is widely used for one-way conduction isolation in circuits with higher signal frequency. It is also commonly used in communications, computers, TV circuits and industrial control circuits.

1N4148 Switching Diode

Specifications

1N4148 Package Dimentions

Figure 1: 1N4148 Package Dimentions

1N4148 Polarity Judgment

The pin on the side with the black ring on the 1N4148 tube is the negative electrode of the diode, and the other side is the positive electrode. As shown below:

Figure 2: 1N4148 Switching Diode

Applications

1. Rectification: Use unidirectional conductivity to convert AC current into DC current. Four 1N4148 diodes are connected end-to-end and directly integrated into an IC to form a bridge stack.

Figure 3: Rectifier Circuit

2. Clamp protection circuit: It consists of two diodes connected in reverse series. The head and tail connections of the two diodes are protected nodes. Taking 1N4148 as an example, when the voltage at this point is >VDD+0.7V, D2 is turned on; and when the voltage at this point is <-0.7V, D1 is turned on. Therefore, the voltage at this point is clamped between -0.7V and VDD+0.7V.

Figure 4: Clamp Protection Circuit

3. Anti-reverse connection circuit: It uses a fuse or 0 ohm resistor and a reverse parallel diode D2. When the circuit is working normally, the diode reverse cut-off does not conduct, and the fuse will not be blown; when the positive and negative poles of the input terminal are connected reversely, D2 is turned on, the current is very large at this time, the fuse is blown, the circuit is cut off, and the subsequent circuit is protected.

Figure 5: Anti-reverse Connection Crcuit

Figure 6: Freewheeling Protection Circuit

1N4148 vs 1N5819 vs 1N4007

(1) 1N4148 is a switching diode with a withstand voltage of 100V, a current of 150mA, a forward voltage drop of 1V, and a fast reverse recovery speed.

1N4148 is a point-contact low-current rectifier with high speed, and the current is only 50mA. 1N4148 and 1N4007 can be temporarily replaced with each other under general small current (below 100mA, reverse voltage below 100V).

(2) 1N5819 is a Schottky diode with a withstand voltage of 40V, forward voltage reduction, and reverse recovery time of about 10ns. It is mainly used in high-frequency circuits:

High-frequency, low-voltage, and high-current characteristics are the differences between 1N5819 diodes and ordinary diodes. It is widely used in circuits such as switching power supplies, frequency converters, and drives, and is used as high-frequency, low-voltage, and high-current rectifiers, freewheeling, and protection diodes. Another use is voltage stabilization-taking advantage of the reverse characteristic. Therefore, when the withstand voltage is low and the current is not large, you can consider using a voltage regulator tube instead.

(3) 1N4007 is an ordinary rectifier diode with a withstand voltage of 1000V, a current of 1A, and a reverse recovery time at the ms level. It can only be used in low-frequency circuits: In addition, because of its large voltage drop and high withstand voltage, it is suitable for high voltage (12V~ 1000V) switching power supply, and it can also be used for voltage stabilization, clamping, one-way conduction and protection circuits.

Conclusion

In circuit design, diodes are very commonly used basic components. Their main functions are anti-reverse, rectification, voltage stabilization, freewheeling, detection, voltage doubling, clamping, envelope detection, etc. As a switching diode, 1N4148 is widely used in one-way conduction isolation. And it is a small-signal high-frequency diode in the market.