A thick-film digital potentiometer

This paper describes a digital potentiometer constructed using thick-film techniques and consisting of a. 16-bit TTL shift register and 16 single pole-double throw FET switches connecting an inverted R-2R resistor network to an operational amplifier. The register and switches are formed from unencapsulated ' chips ' mounted on a 2 in. x 1 in. ceramic substrate. The R-2R'network is formed with thin-film and discrete resistors. Constructional details are given that illustrate the practicality of using a thick-film technique for composite analogue/digital circuitry.