[sdiy] Op Amp selection criteria

[John Mahoney]

Ah, the annual "Which Op Amp?" question. To which I respond with my 
annual, edited summary of replies. :-)


But first, here's a brief excerpt from a review of a Benchmark preamp 
which suggests that the LM4562 is worth investigation for audio use:

"Benchmark has relied on the classic NE5534 and NE5532 integrated 
circuits for their designs, and I expected the same in the MPA1. 
Instead, along with some custom matched input transistors I found 
several National Semiconductor LM4562 dual opamp chips..."


The summary of replies is below. The first two are from Paul S., 
whereas I've lost the attribution on the rest. (Sorry, guys!)

Hope this helps,
John



Paul Schreiber, August 2007:
	For DC summing amps: use a LT1013CN8 from Linear Tech
	For audio, use OP-275GPZ. Those are all the ones BUT the DC summing amp :)
	You may need a 22pf cap across the feedback cap. OK, that is between
		pins 1&2 or 6&7. The resistor has the stripes on it.

Paul later added the following:

Some of those comments are mine, I will reiterate:

a) original post was about S&H circuits. I use the AD82x series from 
Analog Devices. High input impedance, very low drift, low offset. 
They are "expensive", but man o man do they work great.

b) If you want "pure and clean" audio, it's hard to beat a OP275GP 
(also AD). You *need to have* a small (say 22pf) cap across the 
feedback resistor or you will get overshoot.

c) If you want "that 70s sound" use 4558 op amps. NE5532s are good 
for *mic preamps* because if you use resistors over say 5K the bias 
currents will eat you alive :) And they suck power like there's no tomorrow.

d) for just general use, it's next to impossible to discount 
TL072ACPs. Heck, I used over 6,000 last year :)

e) if you want *precision summing*, like for a VCO CV summer, it's 
hard to beat a LT1013 (Linear Tech, www.digikey.com stocks them) and 
some RN55E resistors at 0.1%, 20ppm (www.mouser.com has them 
reasonable). You can build a REALLY GOOD summing amp for the cost of 
a large Starbucks expresso.

Paul S.

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All you need is 2 types:
TL072ACP - audio path
LT1013P - DC summers
both available from DigiKey

--------------------

Hmmm...   I agree with [the above] suggestions, but you asked for 
five ;) I have a number of OP-275 that I use for audio -- very fast, 
low noise, and high current.  I use the LT1013 for precision 
voltages, but they are slow.  I have a bunch of SSM2135 that I use 
for single-sided (9V battery audio applications) and you should have 
a fast op-amp that can work single sided if you plan on building 
stomp-boxes.  However, the op-amp I use the most, is the TL072 -- 
fine for summing non-critical voltages, inverting signals, creating 
high-impedance inputs, driving LED's, and as an output amp for gates, 
triggers, LFO's, envelopes, etc.  The fifth op-amp is the unusual 
LM3900 "Norton" amplifier used in a number of different applications. 
Since through-hole parts are becoming more difficult to find, some of 
these might now be obsolete.

--------------------

Analog Devices OP275GP is very good
Burr-Brown OPA2604/604 is very good
replace tl072 opamps with ne5532   <--- this has been questioned, 
perhaps for current consumption reasons
replace 741 with 411
replace LF324 with TL074

--------------------

I swapped the TL074 with a TLE2074. I perceived slightly higher gain 
before it distorts and a fuller low end.

--------------------

...looking for a replacement to a TL074.  I suggested the Motorola 
MC33079 chip. I like the sound of the 33078 in stereo bus applications.

--------------------

Good: OP275GP (Analog Devices)
Better: AN797 (Analog Devices)
Best: OPA627P (TI/Burr-Brown)
Best bang-for-the-buck: TL072ACP (TI)  [see also TL072BCP]
Best choice for cheap: NJR4580D (JRC)
World's cheapest: NJR4558D (under 10 cents in 5,000 pieces)

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