Frequently Asked Questions about Rotary Encoders

Dedicated ICs are used for both the sending side (driver) and the receiving side (receiver) to transmit signals with greater power. An inverted polarity signal is output relative to the output signal, and this difference is used as the signal (differential output). This is a data transmission method that complies with the EIA RS-422A standard.

The totem pole, open collector, and collector output use the potential difference between the signal line and COM as the signal. Therefore, if noise voltage is applied to the COM side, the potential difference with the signal line decreases, making it difficult to determine High-Low and increasing the likelihood of transmission errors. In contrast, the line driver output outputs a signal with an inverted polarity relative to the output signal, using this difference as the signal (differential output), which prevents the potential difference from becoming small and tends to be more resistant to noise.

Line driver output circuit

line driver output signal