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Jellybean op amps

We've been going back and forth on the LM324/358 etc. recently. One of my lowish-noise, low cost faves has long been the bipolar MC33078/9, whose decent combination of noise, bandwidth, cost, DC performance, and output swing is fairly stellar at about 20 cents in reels, just a bit more than a knockoff TL084. (*) It isn't a true single-supply op amp like the 324, but on the other hand it actually works at AC. ;)

TI recently introduced the OPA1678/9, which are some sort of weird CMOS riff off the old Motorola chips, and are sort of interesting. They're twice the price, but a 40-cent quad won't break the bank for most of us. The specs are quite similar, except for the improved input bias current and lower distortion. (The 33079's 800-nA maximum bias current and 500 fA/sqrt(Hz) current noise are pretty annoying in some applications.)

The OPA1678/9's bias and offset currents are ~10 pA at low temperature, but go nuts above 25C, getting up into the nanoamps at 85C. That's not horrible for a JFET, but since it's a CMOS part, I gather that something funky is happening with the input protection circuitry.

Anyway, one for the tool kit. Anybody used it?

Cheers

Phil Hobbs

(*) Avnet claims to be selling the ST Micro TL084 for 5.6 cents in reels--cheaper than an LM324A!

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com
Reply to
Phil Hobbs
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We use some OPA171s which look very similar, same bias current effect at temperature. Nice little EMI hard part. Well behaved.

1.4 cents per opamp. That's insane. These used to cost over $100 each, when $100 was worth a lot.

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--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com
Reply to
John Larkin

The closest I use to a jelly bean is the LT1013, my goto single supply opamp.

George H.

Reply to
George Herold

I'm also a fan of LT1013, only 150uV offset. But it had the usual high LTC price, until TI offered a 2nd source. But now TI's price is as high as the LTC / AD's price, maybe even higher, $3.43 qty 100.

--
 Thanks, 
    - Win
Reply to
Winfield Hill

The step-up bipolar jellybean from the LM324 I like is the STMicro TS462. Lower max supply voltage, GBW (12 vs 16), and slew rate (4 vs 7) than the MC33078. Worse max offset voltage than the MC33078 5mV vs. 2.

Lower input bias current, lower noise, operates down to +/- 1.25 volts, and RRIO. Approximately the same price in quantity

Reply to
bitrex

correction they're RRO not RRIO

Reply to
bitrex

5.6c a quad is too much :)

Prices have come down since Babbage's machine too. Didn't he need a national government to bankroll him?

NT

Reply to
tabbypurr

Bob Pease gave its price over much of its mid-century life (1950-1970?) as $22, about $100 in 2019 dollars.

If the same essential design was on sale at that price for 20 years, at that time (before my time...) I don't know, but by about 5 years in it was already overpriced and under-performing. Ahh, backwards-compatibility market.

Adding one or two germanium PNPs available by the mid-late-50s to the circuit making it a hybrid I think could've probably lowered costs and boosted gain/bandwidth performance significantly while keeping the other compatibility specs the same, but hindsight is 20/20 I guess

Reply to
bitrex

Reference:

Reply to
bitrex

I used a few of those K2-W tube op-amps, when I started at Harvard in Chemical Physics, in the mid 60s. Their high output voltage was very convenient. Later we used semi op-amp modules. Then came the uA702 (arggh, all-NPN, +12 -6V supplies, +/-3.5 volt swing into 10k) and the uA709. Finally things started to settle down with the LM301 and uA741. I made a slow ramp integrator using uA741, IIRC, but it suffered from crazy offset-voltage jumps, soon enough we learned about popcorn noise!

--
 Thanks, 
    - Win
Reply to
Winfield Hill

Yes, it's not even single supply, that's pretty limiting for a low-V op-amp.

--
 Thanks, 
    - Win
Reply to
Winfield Hill

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