Unity gain stable so should not be oscillating... these uber op amps draw 10+mA so over 1/3 Watt of heat dissipation with +/- 15v rails, with load even more heat.
JR
OUTPUT DRIVE AND STABILITY
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APPLICATION HINTS
The LME49990 is unity gain stable from both input (both stable when gain = -1 or gain = 1). It able to drive resistive load 600Ω with output circuit with a typical 27mA. Capacitive loads up to 100pF will cause little change in the phase characteristics of the amplifiers and are therefore allowable.
Capacitive loads greater than 100pF must be isolated from the output. The most straight forward way to do this is to put a resistor in series with the output. This resistor will also prevent excess power dissipation if the output is accidentally shorted.
The effective load impedance (including feedback resistance) should be kept above 600Ω for fast settling. Load capacitance should also be minimized if good settling time is to be optimized. Large feedback resistors will make the circuit more susceptible to stray capacitance, so in high-speed applications keep the feedback resistors in the 1kΩ to 2 kΩ range whenever practical.
OUTPUT COMPENSATION
In most of the audio applications, the device will be operated in a room temperature and compensation networks are not necessary. However, the consideration of output network as shown in Figure 28 may be taken into account for some of the high performance audio applications such as high speed data conversion or when operating in a relatively low junction temperature. The compensation network will also provide a small improvement in settling time for the response time demanding applications.
Figure 28. LME4990 Output Compensation Network
SUPPLY BYPASSING
To achieve a low noise and high-speed audio performance, power supply bypassing is extremely important. Applying multiple bypass capacitors is highly recommended. From experiment results, a 10μF tantalum, 2.2μF ceramic, and a 0.47μF ceramic work well. All bypass capacitors leads should be very short. The ground leads of capacitors should also be separated to reduce the inductance to ground. To obtain the best result, a large ground plane layout technique is recommended and it was applied in the LME49990 evaluation board.