A Brief Overview on Discrete Semiconductor Products

Discrete semiconductor products play a crucial role in ensuring proper signal regulation, switching, and protection across countless electronic systems. Among these types of components, DIACs and SIDACs offer specific utility in triggering and control applications, particularly within circuits requiring precision and protection. These variants may not receive as much attention as transistors or integrated circuits, but their function is indispensable in various electrical and electronic infrastructures. In this blog, we will cover everything you need to know about what DIACs and SIDACs are, as well as how to determine which type is more suitable for different scenarios.

What is a Diode for Alternating Current (DIAC)?

DIACs are bidirectional trigger diodes designed to conduct current only after their breakover voltage is reached, allowing them to remain in a non-conductive state during normal circuit operation. Once that specific voltage threshold is met, a DIAC will sharply switch to a low-resistance conducting state so current may pass through in either direction.

As they exhibit nearly identical voltage thresholds for conduction in both the positive and negative directions, DIACs help produce more uniform and stable firing angles when managing alternating current (AC) signals. This symmetry means that the device responds consistently regardless of the polarity of the AC cycle, resulting in smoother and more predictable phase control. As a result, DIACs are especially useful in applications that require precise regulation of power. They are often used in conjunction with TRIACs - also known as bidirectional triode thyristors—to provide more controlled triggering in AC power circuits.

What is a Silicon Diode for Alternating Current (SIDAC)?

SIDACs are also bidirectional semiconductor devices with similar behaviors to DIACs, but they are capable of handling much higher voltages and currents. These variants offer more robust conduction properties and are better suited for applications that demand higher energy dissipation or protection against transient voltage spikes.

A SIDAC will remain non-conductive until its breakover voltage is exceeded. At that point, it undergoes a sudden drop in resistance so a significant amount of current passes through. Once the current falls below the holding threshold, the SIDAC returns to its original non-conducting state. This makes it ideal for applications involving overvoltage protection, crowbar circuits, and surge suppression in sensitive electronics.

Comparing DIACs and SIDACs

Although DIACs and SIDACs share some functional similarities, their distinct electrical characteristics and design parameters lead them to serve different roles in electronic systems.

DIACs are best suited for scenarios such as:

• Triggering TRIACs in AC dimmer circuits, where they help initiate conduction at specific points in the AC waveform
• Light dimming systems for residential and commercial lighting, where stable and repetitive triggering is needed
• Basic phase control in small motor applications, such as fan speed control
• Power regulation systems that require low-voltage triggering, generally in the range of 25V to 40V

Meanwhile, SIDACs are more appropriate for:

• Surge protection in communication and power systems, where their higher breakover voltage allows them to block normal voltages but quickly conduct during overvoltage events
• Overvoltage suppression in telecom and industrial control devices to protect sensitive components
• Ignition circuits in gas-discharge lamps, where a high-voltage pulse is required to initiate conduction
• High-voltage pulse generation for test equipment, as their sudden breakdown and conduction can initiate controlled discharges

Considerations for Implementation

Once you have decided if a DIAC or SIDAC best meets your requirements, the task does not end there. When integrating either of these items into system architecture, there are a few factors to keep in mind in order to ensure their effective use.

For instance, these components—particularly SIDACs—may dissipate significant energy during operation, necessitating proper heat dissipation techniques. Similarly, voltage tolerance must be carefully matched to the system's characteristics to avoid premature triggering or delayed response. Even though modern DIACs and SIDACs are typically very robust, extreme temperature swings or prolonged exposure to high voltage can degrade them over time. As such, appropriate environmental ratings and certifications should be verified during the component selection process.

Component tolerance is also important to contemplate. Manufacturing variations may result in slight differences in breakover voltage across devices of the same model, which could affect precision applications. This is why it is often advised to test components within the specific circuit during the development phase.

Secure Quality DIACs and SIDACs from ASAP Semiconductor

In conclusion, reliable, high-performance discrete semiconductors like DIACs and SIDACs are vital in various systems, so it is essential to source them from a trusted procurement partner that presents quality and traceable products. ASAP Semiconductor stands out as a premier distributor for these needs, offering a vast selection of top-quality DIACs, SIDACs, and other discrete semiconductors.

Through our website, we present parts sourced exclusively from dependable manufacturers and verified suppliers, all of which are subject to rigorous quality assurance measures prior to shipment. This reduces sourcing complexity by ensuring all of our customers receive components that meet the exacting standards required in demanding applications, all on one platform. Furthermore, we are prepared to meet all of your operational goals with competitive, swift, and tailored procurement solutions when you kick off the purchasing process with us. Bearing all of this in mind, do not hesitate to reach out to our experts to see how we can serve you.