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Logatithmic Amplifier


Analog multiplication can be carried out with a basic circuit like that of Fig. 9-7. Essential to the operation of the logarithmic amplifier is the use of a feedback-loop device that has an exponential terminal characteristic curve; one such device is the semiconductor diode of Chapter 2, which is characterized by

iD = I0 (e VD / hVT - 1 ) @ I0  e VD / hVT 
Logarithmic amplifier

A grounded-base BJT can also be utilized, since its emitter current and base-to-emitter voltage are

related by

iE = IS e vBE / vT

Keywords : Amp, Opamp, Logaithmic, Amplifier
Writer : delon  |
15 Jul 2006 Sat   
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