LM13700 question

[Colman]

hi everybody. is the LM13700 the same as the LM13600?
pinout seems the same and they are both transconductance amplifiers with linearizing diodes.for what i gather TI retired the 13600 and issued the 13700 after.
thanks in advance.
Aharon


ps:i want to use it on the engineer's thumb.


http://www.valvewizard.co.uk/engineersthumb.pdf

https://pdf1.alldatasheet.com/datasheet-pdf/view/8638/NSC/LM13600.html

https://www.ti.com/lit/ds/symlink/lm13700.pdf

[duck_arse]

nvrmnd

[Mark Hammer]

I would also like to know the contexts in which a 13700 should/must be used, rather than a 13600.

[Colman]

duck_arse and Mark Hammer,done .
Hey Mark haven't talked to you since that day I tried to find you at the Sound of Music ,that must've been 2006/2007.

[PRR]

From the datasheet that you linked:

The output buffers of the LM13700 differ from those of the LM13600 in that their input bias currents (and thus their output DC levels) are independent of IABC. This may result in performance superior to that of the LM13600 in audio applications.

[Colman]

Thanks PRR ,but for the compressor won't make a difference right?
Aharon

[PRR]

https://www.diystompboxes.com/smfforum/index.php?topic=32660.0
https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/769406/lm13700-what-is-function-difference-between-lm13600-and-lm13700
http://www.idea2ic.com/LM13700.html
http://www.synthdiy.com/files/2007/LM13600-LM13700.htm

[Colman]

Thanks again PRR for that link.
It seems like the chips are close enough for rockn'roll,taking into consideration that they are the same chip, the 13700 was issued as a replacement after the 13600 was discontinued+an slight improvement.
I'm not quibling about prices here I just happen to have 13600s at home.
I will try it and report back, tomorrow I will go and buy PNP paper and make a DIY board in the meantime maybe Mark will chime in or duck_arse( maybe even Merlin)
Thank you very much PRR.
Aharon

[Colman]

I went to Melvin's site and found out that the 13600 will work, the part that's different is not connected for this,thanks for the help guys.
Aharon

[DrAlx]

https://www.diystompboxes.com/smfforum/index.php?topic=97123.msg1181190#msg1181190

See above post. LM13600 will give the problem I describe if you build the version 4 circuit.
See Merlin's suggestion in follow up reply to that post about not using the output buffer (i.e. doing something similar to the version 2 circuit).
In the end I swapped out the 136000 for a 137000.

[Mark Hammer]

duck_arse and Mark Hammer,done .
Hey Mark haven't talked to you since that day I tried to find you at the Sound of Music ,that must've been 2006/2007.

What city would that have been in?  I'm blanking.

[Colman]

Burlington,Ontario.
Aharon

[merlinb]

I went to Melvin's site and found out that the 13600 will work, the part that's different is not connected for this,thanks for the help guys.

Yes it will work in the version 3 circuit since the buffer is not used: http://valvewizard.co.uk/engineersthumb3.html
The buffer is used in version 4 but I haven't tried an LM13600 in version 4, so I don't know how it would fare there, but I suspect not ideal

[Mark Hammer]

Burlington,Ontario.
Aharon

And the Sound of Music would have been that annual festival near the beach?

[Colman]

Exactly Mark and I looked backstage of the country bands and I could not find you.
Aharon

[Colman]

I went to Melvin's site and found out that the 13600 will work, the part that's different is not connected for this,thanks for the help guys.

Yes it will work in the version 3 circuit since the buffer is not used: http://valvewizard.co.uk/engineersthumb3.html
The buffer is used in version 4 but I haven't tried an LM13600 in version 4, so I don't know how it would fare there, but I suspect not ideal

Thanks Merlin, I'm building this version:
http://www.valvewizard.co.uk/engineersthumb.pdf

hope it works.

Aharon

[Mark Hammer]

Exactly Mark and I looked backstage of the country bands and I could not find you.
Aharon

Must have been something I wanted to get to but family itinerary precluded it.

[PRR]

...they are the same chip, the 13700 was issued as a replacement after the 13600 was discontinued+an slight improvement.

They seem to be from the same time and hand. They are both in my 1987 book, not in my 1985 book. (I have gaps and they may be in a supplement or sumthin I missed.)

Here's the official bumph. I sense there is more behind the scenes, maybe insufficient process control (leakage or gain at low currents).

[Rob Strand]

I know I've gone through this in the past.   My first guess was for speed (at low IABC).

Here's the official bumph. I sense there is more behind the scenes, maybe insufficient process control (leakage or gain at low currents).

The opening blurb on the LM13700 datasheet says:

"The output buffers of the LM13700 differ from those of the LM13600 in that their input bias currents are independent of IABC. This may result in performance superior to that of the LM13600 in audio applications."

The real question is: Why does the LM13600 have a variable buffer current in the first place?

The LM13600 claims is the buffers are "Controlled Impedance",  there is a section in the LM13600 datasheet which highlights three points:

"Controlled Impedance Buffers
***1 The upper limit of transconductance is defined by the maximum value of IABC (2 mA). The lowest value of IABC for which the  amplifier  will  function  therefore  determines  the  overall dynamic range. At very low values of IABC, a buffer which has very low input bias current is desirable. An FET follower satisfies  the  low  input  current  requirement,  but  is  somewhat non-linear for large voltage swing.

***2 The controlled impedance buffer is a Darlington which modifies its input bias current to suit the need.
For low values of IABC, the buffer's input current is minimal. At higher levels of IABC, transistor Q3 biases
up Q12 with a current proportional to IABC for fast slew rate.

***3 When IABC is changed, the DC level of the Darlington output buffer will shift. In audio applications where I
ABC is changed suddenly, this shift may produce an audible "pop". For these  applications the LM13700 may
produce superior results"

So without analysing too deeply:
- better tracking at low ABC, more accuracy
- better speed at low IABC   ; note the datasheet shows the same slew-rate for both but that's at IABC=500uA
- trade-off/side-effect is the pop, which is undesirable for audio where IABC changes quickly.