Single Supply Operation With Power Op Amps

The article outlines the problems and solutions for operating power op amps with a single high power supply voltage. Several application circuits are proposed that may help the user reduce system costs while maintaining high performance. Some familiarity with op amp circuits is assumed. Although this article assumes some knowledge of operational amplifiers it may be beneficial for some readers to review a brief refresher on op amp theory. Other readers may feel free to skip to page 3. Today's operational amplifiers, whether constructed from discrete components or a monolithic chip, approach many of the characteristics of the ideal differential gain block of Figure A. The ideal differential gain block is characterized by infinite gain and bandwidth, infinite input impedance, zero output impedance and zero differential input error. These characteristics imply that the overall performance of an application circuit is determined by the external components connected to the op amp. In all high performance electronic circuits the physical layout of the circuit is of paramount importance. This is no less true in power op amp circuits where small input signals and high voltage, high current output signals exist side by side. Fortunately, if a few simple suggestions are followed a successful application circuit layout is assured. The first step in assuring that a good motherboard layout is achieved actually involves the power op amp itself. At Power Amp Design the motherboard layout is considered when the amplifier model is in development. The pin-out of the amplifier is arranged to help the motherboard designer achieve a good layout.