LM4780 Chip Amp
LM4780 Chip Amp
LM 4780 Chip Amplifiers
Thursday, November 29, 2012
The amplifiers currently powering my main stereo system are based on the National Semiconductor (now discontinued) LM4780 stereo power amplifier chip. Using printed circuit boards from AudioSector, heat sinks from old JBL amps, and other parts from my stash, they went together pretty easily. Unfortunately, these excellent IC amplifiers have been replaced with class-D chips which are more efficient, but not as clean and flat in response.
http://www.audiosector.com/lm4780
The circuit is a straight DC- coupled power op-amp. No input capacitors, no output Zobel network.
As simple and direct as it can get. There have been no stability or offset problems.
The Cs supply bypass caps are parallel groups of 4700 mF + 10 mF + 0.1 mF + 0.001 mF electrolytics and ceramics to maintain a very low ESR from audio to RF.
Power supply is bipolar full wave off a center-tapped transformer with a group of parallel filter capacitors and MUR860 diodes. Simple stuff again.
So here’s what they look like. To tell them apart, each has a different color power LED.
Built around a National Semiconductor LM4780 stereo amplifier chip.