General Description. The AS and AS are junction isolated ultra well- matched monolithic NPN transistor pairs with an order of magnitude improvement in. LM/LM Supermatch Pair. General Description. The LM and LM are junction isolated ultra well- matched monolithic NPN transistor pairs with an. LM datasheet, LM circuit, LM data sheet: NSC – LM/LM Supermatch Pair,alldatasheet, datasheet, Datasheet search site for Electronic.

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By using our site, you acknowledge that you datashedt read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. The traditional logarithmic amplifier circuit is described in National Lm3944 This circuit uses the difference of two transistor currents to generate the log of the input over a pretty wide range. The well-matched transistor pair Q1a and Q1b are halves of the LM “supermatch” transistor pair. But National discontinued this part last year with no clear replacement. I can use LM array, but the specs are far worse.

There are plenty of arrays of ‘ or ‘ available, but there is no mention of matching in the datasheet. The transistors might be on separate dies for all I know. TI still sells some Burr Brown log amps but they are expensive. It seems that this is not recommended for new designs but the replacement is the MAT How about the LS from Linear Systems? The chip has almost the same name: The specs are identical to the original. You can find them here But the plant does dattasheet sell them directly.


You have to find the dealer in Moscow can find an email or lm3944 in case someone need it.

I had this idea for a quick and dirty log amp. If you modulated the reference voltage by 3dB, the output would probably average to about the right value. That would more-or-less be an interpolation between 3dB values.

This is probably not the way to go unless there is a need for an LED bargraph in the circuit already. This circuit looks to be a log amplifier using two op-amps, two transistors, a few passives and a current source. Datawheet, I’m not sure how suitable it is for your application.

LM Datasheet, PDF – Alldatasheet

Intersil makes a number of transistor arrays some are certainly single die and well matched. TI has a bunch of chips that implement log amps. I don’t know what the definitive chip is but there are many chips that implement the whole circuit. Devices equivalent to the LM are now being made by another company: Thank you for your interest in this question. Because it has attracted low-quality or spam answers that had to be removed, posting an answer now requires 10 reputation on this site the association bonus does not count.

Would you like to answer one datashest these unanswered questions instead? Home Questions Tags Users Unanswered. What is the new standard log amp circuit? How can I cheaply make a logarithm?


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MikeJ-UK 5, 11 MAT12 is still in production, but octopart. So datasyeet cheaper than the LOG Chris Johnson datashwet That’s an interesting forum thread, especially the story about MAT Two LMs can be stacked to get 60 dB range. I just get the default circuit.

Especially in this circuit, which lives and dies by transistor matching, the simulator is going to give a very optimistic performance estimate. Those “transistors” are identical. I tried adjusting the Hfe of the transistors and unless it was something like it kept a very clean log output.

I’m not sure to what extent other parameters would matter, though. Joseph Perkins 1 1. TI still lists the part in their catalog, but designates it as obsolete.

There datsheet no commitment that if you design it in to your circuit, you will be able to purchase it later. TI datashewt making the part at all as far as I can tell. They are just listing the National Semi datasheet as a courtesy since they bought National.

As usual, Maxim parts do not exist. Octopart is not comprehensive. For example, does not search Maxim-Direct, i. Maxim direct is saying 15 weeks lead time for single parts.

So Maxim doesn’t have any either. I’d rather the LOG and skip the Maxim hassle.

Roman has mentioned that component.