Current Mirror Design for Low-Power, High-Precision Circuits: Achieving pA-Range Output Currents and High Output Impedance

The current mirror (CM) is a fundamental building block in analog circuit design, primarily used to replicate a reference current at the output terminal, ensuring that the output current closely matches the input current. CMs are crucial in integrated circuits, performing tasks such as current steering, biasing, and active load implementation. In an ideal scenario, the output current should precisely mirror the input current, while the output impedance should be infinite to prevent any loading effects. Thisstudy presents a novel CM circuit design that achieves ultra-low output currents in the picoampere (pA) range, while maintaining an exceptionally high output impedance of around 20 gigaohm (GΩ) range, making it highly suitable for precision applications. The proposed circuit uses 2N7002 N-channel MOSFETs (NMOS), which provide significant advantages in Very Large-Scale Integration (VLSI) due to their low power consumption, compact size, and faster switching speed compared to traditional BJTs. Simulation and verification of the results were carried out using Cadence OrCAD X Capture, demonstrating that the proposed CM circuit effectively delivers pA-range output currents with a high degree of accuracy relative to the input current, while maintaining GΩ-level output impedance. These characteristics make it highly effective for applications requiring precise current replication and high resistance, such as analog signal processing and low-power devices.