An Auto-Zero Comparator for Monolithic GaN Power Integration

Comparators are vital building blocks for integrated power electronics. Monolithic integration of switches and drivers in high-voltage GaN processes have shown significant performance benefits, while analog circuits still fall behind due to offset and noise. An auto-zero comparator design optimized for propagation delay, noise and offset voltage is proposed. It employs multiple AC-coupled gain stages, which are zeroed sequentially to reduce input referred offset and low-frequency noise. Simulations of the proposed comparator are performed using noise and mismatch models extracted from a physical reference design and manufactured test structures. The proposed design achieves 81 dB of gain with 9.3 ns propagation delay. Monte Carlo and noise simulations yield a 1-σ offset of 1.2 m V and 18.2 µV <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</inf> integral input noise.