High Speed Op Amp Query

[Bill_Marsden]

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.

[SgtWookie]

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.

[thingmaker3]

Will this one be fast enough? http://focus.ti.com/lit/ds/symlink/ths4303.pdf

[Papabravo]

I'm kinda partial to the TL081/TL082/TL084 and its cousins the TL071/TL072/TL074

[SgtWookie]

Originally Posted by Papabravo

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]

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".

[Papabravo]

Originally Posted by Audioguru

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.

[SgtWookie]

That's just one of the nice things about the LT1057. It's protected against phase reversal.

[Papabravo]

Originally Posted by SgtWookie

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

TL082 is $0.44
TL072 is $0.50
LF353 is $0.50

[SgtWookie]

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.