Precision improvement in current-mode winner-take-all circuits using gain-boosted regulated-cascode CMOS stages

32×32 winner-take-all matrix with single winner selection

“…An interesting and efficient, yet very simple, alternative to the WTA original circuit [4] is the one proposed by Sekerkiran et al in [5]. Using a gain-boosted regulatedcascode configuration composed of transistors MP1, MP2 and MP3, and current source IPol, the impedance at WTAout node is highly increased.…”

“…In a matrix organised cell core, simultaneous vertical and horizontal inhibition signals are propagated when the first winning cell is found so that only one single digital output is in high state pinpointing a single global winner. Using the analogue WTA circuit proposed in [5] implemented in 0.35 mm CMOS technology, resolutions as high as 10 nA can be achieved, and together with the proposed digital logic a single winner can be obtained every 1 ms time interval. The simulated matrix could be used as the core for the VLSI implementation of an SCD strategy in a neuromorphic vision chip [2].…”

“…Common applications can be found in neural networks or neuromorphic vision analogue VLSI hardware implementations [3]. Since their introduction by Lazzaro et al [4] WTA circuits have suffered several modifications (see [5,6] amongst many others), some focused on improving resolution, time response and power consumption of the circuit, others on controlling its excitatory, inhibitory or hysteretic behaviour. Given the always limited discrimination ability of the WTA circuit a large number of cells increases the probability of having a certain number of cells competing with equal credentials; in this way, multiple winners at the output nodes of the WTA amplifiers can be observed.…”

“…1. The analogue subcircuit is a PMOS version of the one proposed in [5]. The digital logic finds the first analogue winner output and propagates an inhibition signal for the rest of the competing cells.…”

“…2). WTA analogue circuit description: The analogue WTA subcircuit architecture replicates [5], making use of p-channel devices because of different current polarities in the light sensing circuitry. The basic WTA circuit is formed by transistors MP1 and MP4 with current sources ITail and Iin.…”