design problem

Papabravo

Joined Feb 24, 2006
14,410
What is the application for an amplifier whose output is an exponential function of it's input? If this is just an academic exercise, then why bother?
 

hgmjr

Joined Jan 28, 2005
9,029
Go to National Semiconductor's Website and search for application note 311.

This app note has some very good information on log and anti-log amplifier theory along with some example circuits.

hgmjr
 

Papabravo

Joined Feb 24, 2006
14,410
So App Note 311 has a use for an exponential amplifier, and describes a gas guage application that uses an ultrasound pulse to determine fuel level. The anti-log amplifier allows increased resolution as the tank approaches empty. These were for pumps in an irrigation system.

The app note was published in 1991 and DSP has come a long way since then. The other clue to the application's antiquity was the use of 74Cxxx logic at a Vcc of 15 volts. This stuff dates to the 1974 time frame.

This certainly wins my vote for obscurity, but possibly there is a useful pearl in there.
 

hgmjr

Joined Jan 28, 2005
9,029
So App Note 311 has a use for an exponential amplifier, and describes a gas guage application that uses an ultrasound pulse to determine fuel level. The anti-log amplifier allows increased resolution as the tank approaches empty. These were for pumps in an irrigation system.

The app note was published in 1991 and DSP has come a long way since then. The other clue to the application's antiquity was the use of 74Cxxx logic at a Vcc of 15 volts. This stuff dates to the 1974 time frame.

This certainly wins my vote for obscurity, but possibly there is a useful pearl in there.
Admittedly, All true:) .

hgmjr
 
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