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|previous: Dave James The 4739 is a dual op-amp but may n... -- 8/26/1999 1:05 AM||View Thread|
|8/26/1999 6:04 PM|
|Mark Hammer||Re: RC4739 Dual op-amp|
The 4739 comes in two flavours: internally compensated (XR, RC) and noncompensated (uA). I have a bunch of the noncompensated Fairchild chips and never really figured out how to compensate appropriately. Any advice would be appreciated.
As far as I know, there is a chip numbered LM1303 or something like that, which is an identical pre-amp chip, or rather, I have seen numerous schematics for RIAA phono pre-amps that list the 1303 and 4739 and use the identical pinout.
Is there something special about the 4739? Yes and no. In an article in DEVICE, Craig compared a variety of op-amps for noise characteristics under different loads. BiFets (TL072) and MosFets (CA3140) came up strong under high impedance loads and weak under low impedance, as you can imagine. 5534's came up strongest when all the resistors tacked onto the circuit were low values. 4739's were pretty much the best all round chip, though. Not superlative, but always a contender under any load. They slew at 1V/uS, which is certainly better than garden variety 4558's, though not as good as BiFet's or MosFet's. I suspect that the non-functional pins in the middle of each side (output and input pins are separated by a few) also lent the 4739 to easier PC layout, back in the days when autorouting was not widely available. Right now, I'd say the most distinctive thing about them is their lack of availability and non-competitive pricing.
|Dave James "Right now, I'd say the most distin... -- 8/26/1999 7:44 PM|