Differential Receiver

The differential receiver is a critical sub-circuit within Line Driver/Receiver integrated circuits designed for data transmission over long distances or noisy environments. It functions by receiving two complementary voltage signals (differential signals) transmitted along a pair of wires, comparing their voltage difference, and converting this comparison into a single-ended digital output signal. This architecture inherently rejects common-mode noise picked up along the transmission line, ensuring data integrity. It is a fundamental building block in communication interfaces like RS-422, RS-485, CAN bus, and LVDS.

The receiver typically consists of a high-impedance differential input stage (often using a differential amplifier or comparator) followed by a signal conditioning and output driver stage. It senses the voltage difference (Vdiff = V+ - V-) between its two input pins. If Vdiff exceeds a positive threshold voltage, the output is driven to a logic high state. If Vdiff falls below a negative threshold, the output is driven to a logic low state. Voltages within the threshold window (the receiver's hysteresis or input uncertainty region) leave the output in its previous state, providing noise immunity. This rejection of common-mode voltage variations on both inputs is key to its operation.