The monolithic op amp: a tutorial study

Abstract

A study is made of the integrated circuit operational amplifier (IC op amp) to explain details of its behavior in a simplified and understandable manner. Included are analyses of thermal feedback effects on gain, basic relationships for bandwidth and slew rate, and a discussion of pole-splitting frequency compensation. Sources of second-order bandlimiting in the amplifier are also identified and som(s approaches to speed and bandwidth improvement are developed. Brief sections are included on new JFETbipolar circuitry and die area reduction techniques using transconductance reduction,

Quad configuration for improved thermal design of cascode current mirror

“…The idea of the quad layout originates from one of the first designs of the input stage of an operational amplifier [6]. Each of the two transistors 1 and 2 in fig.1(a) is replaced by two equal transistors in parallel: 1-1' and 2-2' giving rise to the new circuit shown in fig.1(b).…”

A 1-GHz bipolar class-AB operational amplifier with multipath nested Miller compensation for 76-dB gain

“…The transfer function of the combination has three poles. However, when the follower and inverter transistors are balanced, mainly by adjusting so that equals , one pole is exactly cancelled by a zero at (5) And the transfer function is found as shown in (6), at the bottom of the page. The zero disappears when equals .…”

“…The Miller capacitor which is used to split the two poles of the two-stage opamp apart [5], [6] has to be chosen such that the unity-gain frequency is below the second pole. The second pole of the combination is given by (7) An opamp is usually compensated such that the poles reach Butterworth positions when a unity-gain feedback is applied.…”

Feedforward compensation of the amplifier output stage for improved stability with capacitive loads

“…and lead compensation. The first two set the gain-bandwidth product and the slew rate of the amplifier [2]. The third is normally applied in the feedback network to correct for phase lag in the output stage.…”