High-speed Current Comparator Research Articles

A 2.5-W 40-MHz-Bandwidth Hybrid Supply Modulator With 91% Peak Efficiency, 3-V Output Swing, and 4-mV Output Ripple at 3.6-V Supply

We describe a supply modulator comprising a proposed delay-based hysteresis controller, proposed wideband class-AB amplifier, and class-D amplifier for an envelope tracking (ET) power amplifier (PA). We investigate the power dissipation and optimization method of the supply modulator for wideband applications taking into consideration the propagation delay, and show that a controller with zero threshold current not only improves the bandwidth of the supply modulator but also reduces its power dissipation. Based on our investigations, we propose a delay-based hysteresis controller embodying a novel high-speed current comparator whose reference current (threshold current) is zero, thereby achieving higher power-efficiency and simpler hardware. We further propose a class-AB amplifier, which features a high bandwidth and accurately controlled quiescent current. The proposed supply modulator features simultaneously the wide bandwidth (40 MHz), high output power (2.5 W), high peak efficiency (91%), high output voltage swing (3 V), and low output ripple noise (4 mVrms) at 3.6-V supply. The ET PA embodying our proposed supply modulator achieves a high power-efficiency of 41.4% at 28.5-dBm peak output power and 34.4% at 3-dB backoff—a significant >1.6× improvement over the radio frequency PA without the supply modulator.

Low-power high-speed current comparator design

A new current comparator is proposed that is optimised for low power consumption whilst maintaining high speed. This novel comparator design offers a reduction in power consumption of over three orders of magnitude compared with other high-speed designs, and allows picoampere current decisions at kilohertz frequencies. Circuit simulations were performed in Cadence software for a standard 0.35 µm process.

2.8 V asynchronous high-speed current comparator for sequence detection applications

A low voltage, low power current-mode comparator is described. The circuit features a wide dynamic range and very high-speed asynchronous operation and is intended for use in maximum likelihood sequence detection (MLSD) applications.

High performance CMOS current comparator

A new high-speed CMOS current comparator is described. By changing the buffer of an existing comparator from class B to class AB operation, voltage swings are reduced, resulting in greater speed for small input currents. Simulation results employing a 1.6 µm CMOS technology show the response time to a 0.1 µA input current to be 11 ns and the power dissipation to be 1.4 mW, resulting in a five times improvement in speed/power ratio over existing high-speed current comparators.