These are Burr Brown Devices from TI. The BB Chips are excellent devices and High Precision, but a bit more expensive. These can be used when customer demands a Higher Quality and Precision. These are good for High Reliability Industrial Instrumentation. – delabs
From TI Data Sheets –
The XTR101 is a microcircuit, 4-20mA, two-wire transmitter containing a high accuracy instrumentation amplifier (IA), a voltage-controlled output current source, and dual-matched precision current reference.
The XTR106 is a low cost, monolithic 4-20mA, two-wire current transmitter designed for bridge sensors. It provides complete bridge excitation (2.5V or 5V reference), instrumentation amplifier, sensor linearization, and current output circuitry.
The XTR115 and XTR116 are precision current output converters designed to transmit analog 4-to-20mA signals over an industry standard current loop. They provide accurate current scaling and output current limit functions.