Voltage Logarithmic convertor

Atilla · 27th October 2011, 04:43 PM

I saw this while looking into how logarithmic amplifiers work:

A Novel Voltage-to-Voltage Logarithmic Converter with High Accuracy

Has anyone implemented anything similar? The usual log amplifiers seem to require a bit complex thermal compensation, while this idea looks fairly stable.

I need audio signal in, log-scaled voltage out and I've started getting very confused in how to do it. I don't need high-frequency operation that much, neither perfect precision, but I've no idea how bad the standard-issue log amplifier really is.

Frank Berry · 27th October 2011, 06:16 PM

What are you attempting to accomplish?
Audio input and a log d.c. output?

peranders · 27th October 2011, 06:28 PM

http://www.analog.com/static/importe...ets/AD8310.pdf

Atilla · 27th October 2011, 07:50 PM

Yes, exactly that Frank.

Thanks peranders, I just saw that IC and a Maxim IC an hour after I asked. The MAX4206 looks hard to source, but the AD should be easier to find.

Atilla · 27th October 2011, 08:28 PM

I found an AD8307 here, it looks like that'll do fine.

Frex · 28th October 2011, 08:53 AM

Hello Atilla,

Maybe this project could interest you, it's a DIY RMS voltmeter with DC log output
using the AD8307 IC.

Frex.

Atilla · 28th October 2011, 09:43 AM

Thanks a lot Frex, this will help me a lot, indeed. And by the way - great project there!

Frex · 28th October 2011, 02:59 PM

In the case of you would want to build it, i have some bare PCB of this
project available for sale.

Frex.

27th October 2011, 04:43 PM	#1
Atilla Soldering Gun Fanatic diyAudio Member Join Date: Jul 2008	Voltage Logarithmic convertor I saw this while looking into how logarithmic amplifiers work: A Novel Voltage-to-Voltage Logarithmic Converter with High Accuracy Has anyone implemented anything similar? The usual log amplifiers seem to require a bit complex thermal compensation, while this idea looks fairly stable. I need audio signal in, log-scaled voltage out and I've started getting very confused in how to do it. I don't need high-frequency operation that much, neither perfect precision, but I've no idea how bad the standard-issue log amplifier really is.

27th October 2011, 06:16 PM	#2
Frank Berry diyAudio Member Join Date: Sep 2003 Location: Midland, Michigan	What are you attempting to accomplish? Audio input and a log d.c. output? __________________ Frank

27th October 2011, 06:28 PM	#3
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	http://www.analog.com/static/importe...ets/AD8310.pdf __________________ /Per-Anders (my first name) or P-A as my friends call me

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27th October 2011, 07:50 PM	#4
Atilla Soldering Gun Fanatic diyAudio Member Join Date: Jul 2008	Yes, exactly that Frank. Thanks peranders, I just saw that IC and a Maxim IC an hour after I asked. The MAX4206 looks hard to source, but the AD should be easier to find.

27th October 2011, 08:28 PM	#5
Atilla Soldering Gun Fanatic diyAudio Member Join Date: Jul 2008	I found an AD8307 here, it looks like that'll do fine.

28th October 2011, 08:53 AM	#6
Frex diyAudio Member Join Date: Nov 2009	Hello Atilla, Maybe this project could interest you, it's a DIY RMS voltmeter with DC log output using the AD8307 IC. Frex.

28th October 2011, 09:43 AM	#7
Atilla Soldering Gun Fanatic diyAudio Member Join Date: Jul 2008	Thanks a lot Frex, this will help me a lot, indeed. And by the way - great project there!

28th October 2011, 02:59 PM	#8
Frex diyAudio Member Join Date: Nov 2009	In the case of you would want to build it, i have some bare PCB of this project available for sale. Frex.

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