rees@apollo.uucp (Jim Rees) (01/20/86)
I recently needed about 5 watts of audio in a small space, so I went down to the local rat shack and bought a LM383. It is supposed to put out 8 watts or so into a 4 ohm load. I wired it up just like the little diagram on the back, but all it does is oscillate. I played with the negative feedback a bit and even tried a new chip. I re-did the layout to give more separation between input and output, and put in bigger bypass capacitors. Nothing helped. I looked up the chip in a National data book and it gives the same circuit as the one I got off the back of the rat shack package. Does this chip work or not? Has anyone tried it? Is there some easier way to get 5 watts of audio? Distortion up to about 1% is not a problem, and I have a split supply plus/minus 8 volts.
don@umd5.UUCP (01/21/86)
> I recently needed about 5 watts of audio in a small space, so I went down > to the local rat shack and bought a LM383. It is supposed to put out > 8 watts or so into a 4 ohm load. > > I wired it up just like the little diagram on the back, but all it does > is oscillate. > . > . > . > Does this chip work or not? Has anyone tried it? Is there some easier > way to get 5 watts of audio? Distortion up to about 1% is not a problem, > and I have a split supply plus/minus 8 volts. You say you looked at the National Semiconductor Handbook and you've got your LM383 hooked-up the same way ?? My Handbook says use a single positive supply, not a split supply... Futhermore, the Handbook says, ".. the amplifier is unconditionally stable for all values of closed loop gain ..". Try the single supply -- bet it works! Enjoy Aural Hedonism !! -- --==---==---==-- "What happened ?" "It seems the occipital area of my head impacted with the arm of the chair." "No, I mean, what happened to us ?" "That has yet to be surmised." ARPA: don%umd5@{ maryland.ARPA, umd2.ARPA } BITNET: don%umd5@umd2 UUCP: ..!{ seismo!umcp-cs, ihnp4!rlgvax }!cvl!umd5!don (NOTE: Please mail to umcp-cs!cvl!umd5!don NOT umd5!cvl!umcp-cs!don)
larry@kitty.UUCP (Larry Lippman) (01/23/86)
> I recently needed about 5 watts of audio in a small space, so I went down > to the local rat shack and bought a LM383. It is supposed to put out > 8 watts or so into a 4 ohm load. > > I wired it up just like the little diagram on the back, but all it does > is oscillate. I played with the negative feedback a bit and even tried > a new chip. I re-did the layout to give more separation between input > and output, and put in bigger bypass capacitors. Nothing helped. I > looked up the chip in a National data book and it gives the same circuit > as the one I got off the back of the rat shack package. > > Does this chip work or not? Has anyone tried it? Is there some easier > way to get 5 watts of audio? Distortion up to about 1% is not a problem, > and I have a split supply plus/minus 8 volts. The chip works. The 0.2 uF bypass capacitors from V_s to ground and V_output to ground should be tanatalum to present a good low impedance path. I suspect that you have used some inappropriate bypass capacitors. A brute force large bypass capacitor is not the answer since a crappy 100 uF aluminum electrolytic is not as good as a 0.2 uF tantalum. ==> Larry Lippman @ Recognition Research Corp., Clarence, New York <== ==> UUCP {decvax|dual|rocksanne|rocksvax|watmath}!sunybcs!kitty!larry <== ==> VOICE 716/741-9185 {rice|shell}!baylor!/ <== ==> FAX 716/741-9635 {G1, G2, G3 modes} duke!ethos!/ <== ==> seismo!/ <== ==> "Have you hugged your cat today?" ihnp4!/ <==