Quantizer

A quantizer is an electronic circuit within an Analog-to-Digital Converter (ADC) that performs the quantization step, where a continuous range of analog input voltages is divided into discrete intervals, each assigned a unique digital code. It determines the resolution and accuracy of the ADC by defining the number of quantization levels (e.g., 8-bit, 12-bit, 16-bit) and the step size between levels, directly impacting signal-to-noise ratio (SNR) and dynamic range. Quantizers operate at high speeds to sample and hold input signals, applying a transfer function that maps each analog sample to the nearest digital representation, often using comparators, reference voltages, and encoding logic.

The quantizer works by comparing the sampled analog input voltage against a set of predefined reference voltage levels generated by a resistor ladder or digital-to-analog converter (DAC). Each reference level corresponds to a specific digital code. Using a bank of comparators, the input is simultaneously compared to all reference levels, and the highest reference level that the input exceeds determines the output code. This process, known as flash quantization in high-speed ADCs, or successive approximation in precision ADCs, discretizes the analog signal into binary values based on the ADC's bit resolution, with quantization error inherent due to the finite number of levels.