When less is more: a minimal approach to low-noise circuits

Electronic systems, from brain-monitoring implants to precision sensing devices, rely on an unseen but fundamental element: a stable voltage reference. If this reference drifts with changes in the chip’s process, supply voltage, or temperature, even the most advanced circuit can struggle to detect subtle signals or correctly interpret biological activity.

Engineers have spent years refining these reference circuits, making them less sensitive to process, voltage, and temperature variations, while also reducing noise and shrinking their footprint. Yet the challenge remains – how do you design something stable enough to deliver clear signals, but small and energy-efficient enough for sensitive applications like neural implants?

Researchers from Piteira’s Engineering Group at INL have shown that a simple idea can deliver meaningful results. Instead of adding complexity for noise reduction, i.e. adding more circuitry which implies more area and more power, they asked a different question: could noise be controlled with just a single, simple element?

Piteira’s group proposes a bandgap reference design where noise performance can be tuned using just one resistor placed between two points in the circuit’s core. That single element reshapes how different sources of noise behave, shifting low-frequency flicker noise into a range where it does less harm. In practical terms, the circuit becomes less noisy at low frequencies, not through the addition of filters or amplifiers, but through a clever redistribution of noise at the source.

This approach, published in IEEE Transactions on Circuits and Systems I, challenges a long-standing trend in electronics, where noise reduction often means complex design, larger area and increased power. In implantable medical devices, this is a critical limitation – a component that takes up too much space cannot sit safely in the brain; and a circuit that consumes too much power generates heat, and drains batteries quickly.

By reducing the number of components, the team achieves lower noise and keeps the circuit extremely compact, ideal for applications where every square millimetre matters. The design is also energy-efficient, a crucial requirement for long-term implantable technology. “Instead of relying on corrective techniques like chopper stabilisation or bulky filters, this solution finds balance through minimalism”, adds João Piteira.

“The idea was first validated through simulations, and later fabricated using standard CMOS technology. The results matched the theory: the reference remained stable over temperature, low-noise, low-power, and impressively small.” To the authors’ knowledge, this design also achieves one of the best performance compromises to date in terms of noise, area, and power consumption.

A less noisy circuit helps detect subtle biological signals. A compact design means it can stay inside the body with less risk and less intrusion. And a simpler design means more accessible technologies, ready to scale beyond the laboratory.

This work demonstrates that minimalism can unlock exceptional performance. By using fewer components and reducing noise, the technology becomes lighter, more efficient, and better suited for biomedical applications where it can make the greatest impact.

Text by Catarina Moura, Science Communication Officer
Photography by Rui Andrade, Multimedia Officer