Image Recognition in Analog VLSI with On-Chip Learning

We present an analog-VLSI neural network for image recognition which features a dimensionality reduction network and a classification stage. We implement local learning rules to train the network on chip or program the coefficients from a computer, while compensating for the negative effects of device mismatch and circuit nonlinearity. Our experimental results show that the circuits perform closely to equivalent software implementations, reaching 87% accuracy for face classification and 89% for handwritten digit classification. The circuit dissipates 20mW and occupies 2.5mm(2) of die area in a 0.35 mu m CMOS process.