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Power Supplies and Decoupling

previous Op Amp Distortion
Because op amp PSRR is frequency dependent, op amp power supplies must be well decoupled. At low frequencies, several devices may share a 10-50μF capacitor on each supply, provided it is no more than 10cm (PC track distance) from any of them.
Proper low and high-frequency decoupling techniques for op amps
Figure 1-86: Proper low and high-frequency decoupling techniques for op amps
At high frequencies, each IC should have the supply leads decoupled by a low inductance 0.1μF (or so) capacitor with short leads/PC tracks. These capacitors must also provide a return path for HF currents in the op amp load. Typical decoupling circuits are shown in Figure 1-86 above.
Power Supplies and Power Dissipation
Op amps have no ground terminal. Specifications of power supply are quite often in the form ±X Volts, but in fact it might equally be expressed as 2X Volts. What is important is where the CM and output ranges lie relative to the supplies. This information may be provided in tabular form or as a graph.
Often data sheets will advise that an op amp will work over a range of supplies (from +3 to ±16.5V for example), and will then give parameters at several values of supply, so that users may extrapolate. If the minimum supply is quite high, it is usually because the device uses a structure requiring a threshold voltage to function (zener diode).
Data sheets also give current consumption. Any current flowing into one supply pin will flow out of the other or out of the output terminal. When the output is open circuit, the dissipation is easily calculated from the supply voltage and current. When current flows in a load, it is easiest to calculate the total dissipation (remember that if the load is grounded to the center rail the load current flows from a supply to ground, not between supplies), and then subtract the load dissipation to obtain the device dissipation. Data sheets normally give details of thermal resistances and maximum junction temperature ratings, from which dissipation limits may be calculated knowing conditions. Details of further considerations relating to power dissipation, heatsinking, etc., can be found later posts in this blog.
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