Dynamic range of Log circuit

Discussion in 'Homework Help' started by ali., Feb 23, 2012.

  1. ali.

    Thread Starter New Member

    Feb 23, 2012
    4
    0
    Hello Everyone,

    I’m looking for some help with calculating the dynamic range of the logarithmic op-Amp circuit below. Can someone please direct me?


    You can assume any values. Opamp dynamic range define as follows:

    DR = 20 Log (Vout(max)/Vout(min))
     
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  2. ali.

    Thread Starter New Member

    Feb 23, 2012
    4
    0
    In the following MT-077 TUTORIAL
    http://www.analog.com/static/imported-files/tutorials/MT-077.pdf in Page number 4 mentioned
    "the dynamic range of this configuration (The Diode / Op-Amp Log Amp) is limited to 40-60 dB because of non-ideal diode characteristic, but if the diode is replaced with a diode-connected transistor as shown in Figure 7, the dynamic range can be extended to 120 dB or more"

    Can anyone explain this please? and I would like to calculate the dynamic range for both circuit!!
     
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