Application of active current mirrors to improve the speed of analog decoder circuits

Abstract

Current-mirrors are widely used in the blocks of analog decoder circuits based on the sum-product algorithm. The simple current mirrors, using diode-connected input devices that traditionally have been used are limited in speed when their inputs are loaded with long wires. We present a block diagram for a large (6, 3) LDPC code and an estimation for the largest possible wiring capacitance in this decoder. We show that when active current mirrors are used on the inputs of the equality nodes, their speed is enhanced. The power and speed for a seveninput equality node are simulated with the basic mirrors and with the modified current-mirror circuits. We show through simulations in STMicroelectronics CMOS 90nm technology and with a supply voltage of 0.4V that the power/speed ratio for a 7input equality node can be improved by approximately 50% with the enhanced topology. R 978-1-4244-4480-9/09/$25.00 ©2009 IEEE

A Power-Efficient High-Drive Current Mirror Combining a Regulated Cascode Topology with a Non-Linear CCII-Based Feedback

“…Using an analysis similar to [3], it can be proven that active-input current-mirror topologies (i.e., feedback between input node and gate voltage in Figure 1a) can improve the speed-power ratio with minimal impact on the overall accuracy. Published in [5] in an early version and lately deployed in various applications [6,7], such structures can overcome under certain conditions the technological limit as long as the power consumption of the feedback circuit can be kept moderately low compared to the current-mirror bias itself. In a previous study [8], we have proven that the replacement of the voltage-mode feedback that exists in a standard active-input current mirror by a current-mode circuit (Figure 1b) significantly enlarges the stability domain and increases the maximum speed reachable while offering a supplementary degree of freedom to tune the system response.…”

Improvement of Active-Input Current Mirrors Using Adaptive Biasing Technique

“…1b. It has been proposed to enhance input compliance and speed-power ratio of dynamic current mirrors for various applications such as biostimulators in [4] or signal processing circuits [5]. The structure is based on a shunt-shunt feedback configuration using Operational Transconductance Amplifiers (OTA) around the current mirror.…”