3 - Analogue integrated circuit technology

Abstract

This chapter discusses the technology used within the analog integrated circuits (IC). The technology is determined by the type of transistor used in the IC. The types include bipolar, bipolar with junction field-effect transistor (JFET) inputs, and LinCMOS (linear CMOS) and BiCMOS (incorporating bipolar and CMOS transistors). Devices with the JFET input transistors, but otherwise using bipolar transistors throughout, were developed in the late 1960s. The advantage of the JFET input op-amp was reduced input bias current requirement. The JFET input op-amps were called the BiFET op-amps by Texas Instruments. This name is descriptive enough because it employs bipolar and field-effect transistors. Junction field -ffect transistors were introduced into the op-amp input stages in an attempt to increase the input impedance and reduce the bias current. The intermediate and output stages of the op-amp continued to use bipolar transistors. Digital electronics has been using the CMOS transistors for many years to reduce the size and power consumption of circuits. Power consumption has been reduced by the combination of low-voltage and low-quiescent current requirements. Now analog op-amps use the CMOS for similar reasons.