This post explains for the semiconductor M5218.
The function of this semiconductor is DUAL LOW-NOISE OPERATIONAL AMPLIFIERS(DUAL POWER SUPPLY TYPE).
Manufacturers : Mitsubishi
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The M5218 are semiconductor integrated circuits designed for a low noise preamplifer in audio equipment and a general purpose operational amplfier in other electronic equipment. Two low noise operational amplfier circuits displaying internal phase-compensated high gain and low distortion are contained in an 8-pin SIP, DIP or FP for application over a wide rage as a general-purpose dual amplfier in general electronic equipment.