Digital to Analog Converter A615

Summary: This document is a technical schematic for a Digital to Analog Converter (Model A615) manufactured by Digital Equipment Corporation (DEC). The circuit utilizes ten DEC 7474N flip-flops to process data inputs, which feed into a resistor ladder network through a bank of transistors (Q1–Q10). These transistors serve as switches to convert binary digital signals into corresponding analog voltage levels. The lower portion of the schematic includes additional control and regulation circuitry, featuring transistors Q11 through Q18, various diodes (D1–D27), and a complex network of precision resistors to ensure output accuracy. The design includes power inputs for +5V, +15V, and -15V, as well as ground connections, typical for precision instrumentation of its era.