A monolithic power op amp

Abstract

The standard, junction-isolated power process has been modified by the addition of polycrystalline-film resistors to solve the topological problems encountered in making 90W, 80V, 10A power transistors and connecting them together for a push-pull output. An all-NPN output stage has been developed that holds cross-over distortion to 0.01-percent while driving a 4Ω load, even with the quiescent current below 20 mA. It is stable with all reactive loads and does not have the spurious-oscillation problems observed with the familiar quasi-complementary amplifier. These innovations are described along with the design of a complete power op amp. The all-important safe-area protection is covered in a companion article [1]. Preventing failures from substrate currents arising when the output is driven outside the supply by inductive loads is discussed here.

High bandwidth low power operational amplifier design and compensation techniques

“…A miller capacitor is used to split the poles, which causes the dominant pole to move to a much lower frequency and thus reducing the bandwidth and providing ample stability. This method is featured in the original 741/101 bipolar Op Amps designed by Robert Widlar and was widely implemented henceforth [10]. the RHP zero not only flattens the magnitude response due to the dominant pole but also degrades the phase make it difficult to stabilize the amplifier.…”