Machine learning accelerator

A neural network circuit for providing a threshold weighted sum of input signals, the neural network circuit comprising:

• at least two arrays of transistors with programmable threshold voltage, each transistor of the at least two arrays storing a synaptic weight as the programmable threshold voltage and having a control electrode for receiving an activation input signal, each transistor of the at least two arrays providing an output current for either a positive weighted current component in an array of a set of first arrays or a negative weighted current component in an array of a set of second arrays;
• an associated reference network for each array of transistors configured to provide a reference signal to be combined with the positive weight current component or the negative weight current component of the transistors of the associated array, the reference signal having opposite sign compared to the positive weight current component or negative weight current component of the associated array;
• and
• at least one bitline for receiving the combined positive current component or negative current component, each combined with their associated reference signals.