With their straightforward and cost-efficient approach, Zener diodes are the go-to solution for generating a stable voltage in electronic circuits. Their simplicity eliminates the need for complex integrated voltage stabilizers, such as linear voltage regulators, instilling confidence in their reliability for precise voltage requirements.
Fig. 1 A simple example of decreasing an input voltage towards a lower voltage VOUT using a Zener diode.
Besides reducing an incoming voltage, the potential ripple on the input voltage gets reduced significantly, and the circuit works as a voltage stabilizer. VOUT is supplied to a load where different currents are expected. So, the load is usually a subcircuit and not a simple resistor like depicted in the example circuit. A Zener diode with VZ = VOUT is selected. The series resistor needs to be small enough that VZ can be reached at the highest load current to be expected. A small extra current should be foreseen as a minimum current through the Zener diode to keep the diode in the steep area of the reverse direction I-V-curve and to avoid a noise overlay on VOUT. This minimum current, typically set at 0.5 mA, is crucial for maintaining the Zener diode's stability and preventing noise interference on the output voltage.
Considering these aspects, Rseries can be calculated with the simple equation:
Rseries = (VIN(min) – VZ)/(ILOAD(max) + 0.5 mA)
The highest power dissipation is present at the Zener diode if the load is switched off because all the current flows through the diode. The maximum power PZ(max) possible is calculated according to the formula:
PZ(max) = VZ * (VIN(max) – VZ)/Rseries
Nexperia's BZ* Zener diode series is a versatile solution. It offers a wide voltage range from 2.4 V up to 75 V, with 37 different nominal voltages according to the DIN IEC 60063 E24 series. This variety, combined with the availability of many packages, including leaded SMD and leadless options, empowers designers with a range of choices for their specific application needs, making them feel in control of their design process.
The BZ* families stand out with shallow leakage currents, typically below 1 nA, for voltages below rated Vz.
In addition to the typically 2% and 5% tolerance class of Zener diodes, Nexperia's A-selection offers a 1% tolerance, ensuring precision in reference voltage Applications. This narrow tolerance enables a more accurate realization of the reference voltage, instilling confidence in the design's performance.
Zener diodes focusing on an extremely low leakage current can show a noise overlay to the breakdown voltage. This effect starts for diodes with a nominal VZ of 10 V when the breakdown is mainly supported by an avalanche breakdown and not the name-giving Zener effect. The noise is removed if the Zener current IZ is bigger than ~0.5 mA. If a Zener diode clamps incoming pulses where no bias current is applied, an overswing must be considered. An 'overswing' refers to the phenomenon where the output voltage overshoots the desired level due to the Zener diode's response time. Nexperia offers Zener diodes that do not show this behavior. The PZU* family provides a drop-in replacement solution if an application suffers from overshoots or if a small IZ is foreseen. These diodes are designed to minimize overshoots, ensuring a stable and accurate output voltage.
In conclusion, Zener diodes offer a simple and cost-effective solution for voltage stabilization in electronic circuits. Nexperia's BZ* Zener diode series provides versatility with a wide voltage range and various package options, allowing designers to tailor their choices based on specific application needs. The low leakage currents and precise tolerance classes of Nexperia's Zener diodes further enhance their reliability and performance in reference voltage applications. Additionally, Nexperia's PZU* family of Zener diodes minimizes overshoots, ensuring a stable and accurate output voltage. Overall, Zener diodes present a reliable and efficient method for voltage stabilization in electronic circuits.
Learn more about Nexperia's portfolio of Zener diodes