Researchers identified a 1965 Signetics ST680A integrated circuit by analyzing its silicon die. The chip utilizes diode-transistor logic (DTL) and features four NAND gates. The component was housed in a plastic dual in-line package (DIP), a format introduced by Signetics in late 1965 to simplify assembly and circuit board routing compared to earlier metal can or flat-pack designs.
The analysis revealed that the chip lacked a passivation layer, causing acid used for cleaning to remove the metal interconnects. By examining the underlying silicon, the team reconstructed the circuit layout. The die contains 16 serpentine resistors and bipolar NPN transistors. Each output transistor is capable of sinking 2.5 mA of current.
The study uncovered two unused diodes on the die. This indicates that Signetics used a single silicon base topology for multiple products, including the 670A and 616A models, customizing functionality solely through the metal layer. This approach, known as variFEBS, allowed the company to reduce manufacturing costs by reusing masks.
Signetics was founded in 1961 as one of the first companies dedicated exclusively to integrated circuit production. In 1962, the company launched its first NAND gate product at a price of $125. Facing financial difficulties that same year, Signetics secured an investment of $1.7 million from Corning Glass, which acquired a 51% stake in the firm.
