A significant drawback of classical output stages of microelectronic operational amplifiers, which today are implemented based on BJTs (bipolar junction transistors), CMOS (complementary metal-oxide-semiconductor transistors), or JFETs (junction field-effect transistors), including when these technologies are used together, is that they exhibit a relatively low output voltage slew rate under the influence of large-amplitude pulsed input signals. This undesirable effect is mainly caused by the presence of parasitic capacitances inherent in the reference current source circuits employed and in their output transistors. This paper discusses an original and effective circuit design technique that provides forced recharging of parasitic capacitances, which is used in output stages implemented in numerous patents of the world’s leading microelectronic companies. The introduction of a special differentiating transient correction circuit into the original schematics, as well as various options for its practical implementation, are considered for the first time. The circuitry of such output stages is protected by a patent of the Russian Federation. Four different modifications of buffer amplifiers have been developed and investigated, which are intended for use in modern technological processes implemented with silicon BJT or CMOS transistors, as well as with gallium arsenide n-JFET and p-n-p bipolar transistors. Examples of computer simulation of DC operating modes, as well as transient processes, are presented, which clearly demonstrate a significant increase in the maximum output voltage slew rate (by more than one to three orders of magnitude). The proposed advanced circuit solutions for GaAs transistors are recommended for practical application in microelectronic devices designed for operation under elevated temperature conditions.
Development and design of silicon-germanium (SiGe) analog functional units (operational amplifiers, output stages, etc.) is one of the urgent tasks in modern microelectronics. The use of the combined technological process of SiGe BiCMOS makes it possible to combine in a single integrated circuit the advantages of complementary CMOS triansistors (low power consumption and high integration density) and bipolar heterojunction transistors (HBT) n-p-n type (the ability to operate at high frequencies, low power consumption and, as a result, low intrinsic heat dissipation, high gain, high performance, increased reliability, relatively low cost). To create a micro-power analog component base operating at high temperatures (up to + 250 degrees Celsius), it is necessary to develop special SiGe BiCMOS circuit solutions that take into account the process limitations on the use of certain types of transistors. Four modifications of buffer amplifiers for application as output stages of operational amplifiers, which are oriented to SiGe BiCMOS technological process, are investigated. A program for cataloging and visualization of the considered circuits is developed, which differ from each other by the values of input and output resistances, static current consumption, circuitry of static mode establishment circuits, maximum amplitudes of positive and negative output voltages, etc. Examples of computer simulation of static modes and amplitude characteristics in the Cadence electronics and microelectronics design environment at two temperatures of + 27 and + 250 degrees Celsius are given. The proposed circuit design solutions are recommended for practical use in microelectronic devices operating at elevated temperatures
