High Speed Op Amp Query

Thread Starter

Wendy

Joined Mar 24, 2008
22,145
What is a good cheap modern high speed op amp? It has to have basic DC characteristics, but more than basic stability isn't important DC wise. Cost is important, as is availability. Think a modern 741 (although dual or quad is better).

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OK, started the table, which will likely always be a work in progress. This is obviously very preliminary. Keeping in mind we want this fit a standard page, what other specs are needed? Word of mouth on specs will be accepted.

 

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SgtWookie

Joined Jul 17, 2007
22,210
Have you looked at LF353's? Wide bandwidth (4 MHz) JFET input dual opamps. Cheap. You won't find it at your local Radio Shack, but DigiKey, Mouser, and many other places stock 'em. From Mouser, you could get 10 of 'em for $3.10 + shipping. Checked over at Jameco, for quantities of 5 or more you can get 'em for around $0.17 each.
 

SgtWookie

Joined Jul 17, 2007
22,210
I'm kinda partial to the TL081/TL082/TL084 and its cousins the TL071/TL072/TL074
The LF353 is similar to the TL072, but the TL072's BW is 3MHz, whereas the LF353 is 4MHz.

If you need more bandwidth, take a look at LT1057's by Linear Technology.

If you need LOTS of bandwidth, check out National's LM6152; a dual opamp with rail/rail inputs & outputs and 75MHz GBW product. They'll set you back about $3.50 each in small quantities.
 

Audioguru

Joined Dec 20, 2007
11,249
The TL071, TL072 and TL074 opamps are the same as the TL08x but are selected for low noise. They have FET inputs so have almost no input bias current and very low current noise. They have a bandwidth of 100kHz at full output.
But they have the problem of older FET-input opamps called "opamp phase inversion".
 

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Papabravo

Joined Feb 24, 2006
13,926
The TL071, TL072 and TL074 opamps are the same as the TL08x but are selected for low noise. They have FET inputs so have almost no input bias current and very low current noise. They have a bandwidth of 100kHz at full output.
But they have the problem of older FET-input opamps called "opamp phase inversion".
Absolutely correct.

I have also been burned by a similar problem with an LM324 (PNP inputs), used in a single supply process control application as a unity gain follower, where the input went below the negative rail, and the output went to +Vout(MAX). The quick and dirty fix was a schottky diode clipper on the input.

One problem with the OP is that we lack a precise definition of high speed. Cheap and available we understand.
 

Papabravo

Joined Feb 24, 2006
13,926
That's just one of the nice things about the LT1057. It's protected against phase reversal.
OK, but they are not cheap.
From Digi-Key, $4.50 and $8.75 each in QTY. 1 for the available parts and $2.95 for the SOIC with minimum order quantity of 600 where they only have 282 available. What a laugh riot, I guess if you order 600 they'll ship what they have and back order the rest.

Spot check of other prices for DIP parts
Rich (BB code):
TL082 is $0.44
TL072 is $0.50
LF353 is $0.50
 

SgtWookie

Joined Jul 17, 2007
22,210
I hear you, but look at the other specs.

A 741 op amp is like a '66 Ford Fairlaine straight six with 3-on-the-tree, patched upholstery, rusted floorboards and a burned-out headlight. It might get the job done, but you'll ditch it as soon as you can afford something better.

An LM348 is like a '66 Ford delivery van with bald tires and a busted headlight; bulky and ugly, but just might get the job done.

A TL082 is like a '71 Chevy Chevelle.

A TL072 is like a '71 Pontiac Bonneville (like the Chevelle with the deluxe interior; sound deadening)

An LF353 is like a '72 Olds 442 (quiet like the Bonneville, but faster)

A LM6152 is like a Corvette.

An LT1057 is like a Cadillac Coupe DeVille with a two-tone paint job, chrome wheels, and fuzzy dice hanging from the rear-view mirror.

A THS4303 is like a Formula 1 race car. Not exactly something you'd want to go grocery shopping with, but you'll turn heads in the process.
 
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Papabravo

Joined Feb 24, 2006
13,926
I give you full marks for creativity, but I'm not sure that designers view components in the same way as extensions of their....ahh..er...ego. Yeah ego -- that's the ticket!
 

SgtWookie

Joined Jul 17, 2007
22,210
I just had to have some fun with this thread. ;) I figured vehicles were as good an analogy as anything.

Gotta get me one of those!
Completely off-topic, but worth a chuckle is the mental image you might get when picturing a midnight blue Jaguar XJ-S V12 Convertible (DHC for you Brits) with a trailer (caravan) hitch towing a Sea-Doo (a small, fast watercraft). My spouse did that to the Jag. :rolleyes: Actually backed the wire wheels into the salt water of the Gulf of Mexico. Sacriledge!
 

Thread Starter

Wendy

Joined Mar 24, 2008
22,145
And I bet you're still married to her!

The reason I asked the question is everyone dis's the 741. I like the little chippie, I saw what their made of many times as I managed to not only let the smoke out, but the silicon as well. :) For basic projects I wouldn't hesitate to use it still. But there is always something that needs a higher frequency, and I was curious as to what to use.

I didn't do this particular trick, but when I was in college and 741's were pretty new my instructor needed a +/- power supply (this being LONG before the age of the PC), so he rigged a dual bench supply and used a 3 prong AC outlet for power in a strip running down the lab table, +/- 15VDC I think it was. Anyhow, you guessed it, a student got the power plugs confused. Before that the school provided the protoboards, after that the students had to buy them. Too many stunts where the plastic was melted I guess. About that little accident, I wasn't there at the time, but I hear it was pretty exciting!
 

Thread Starter

Wendy

Joined Mar 24, 2008
22,145
I went to Tanner's and bought myself 10 LM353's for 49 cents each. He even through in some samples of a new op amp, a 4558 replacement, JSR's 6558. I've got to look up the datasheet sometime.

I've been telling Jim, the owner of this shop, about this site. I brought a printout of this thread to shop for some op amps, and I gave him the printout. I also bought over $15 worth of resistors (801 parts are 2 cents each) to finish up my resistor kit as far as I was able.
 

jpanhalt

Joined Jan 18, 2008
9,710
What do you think of the LM6171? It's cheaper than the THS4303 and has better slew rate than the LM6152, plus it has a wide supply voltage range . Maybe it's a 928 S4 Porsche?

John
 

Thread Starter

Wendy

Joined Mar 24, 2008
22,145
Something I might do (with a little help from my friends) is draw up a sample comparison chart for op ams under a $1, with things like unity gain, power supply range, slew rate (I like slew rates for some reason). I might add it to my first post for easy comparisons. What other specs do you think would be needed? Some of the more popular expensive units could be added at the bottom, for comparison. I can't be the only guy to allow himself to get out of date on some of these specs.
 

jpanhalt

Joined Jan 18, 2008
9,710
Here are some suggestions:
Slew rate
Unity gain frequency
Input bias current
Power supply (range)
Input type (FET or bipolar) - may be irrelevant given bias current
Voltage or current feedback
CMRR (?)
Unit price (use Digikey and/or Mouser)
Available packages
Available as single, dual, quad

John
 
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