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LogDC (DC Logarithmic Amplifier)

Symbol

Available in ADS

Parameters

Name

Description

Units

Default

VoltSlope

Gradient of transfer characteristic

V/decade

1.e-3

VoltIntercept

Vin for zero output

V

1.e-3

Z1

Reference impedance for port 1

Ohm

50

Notes/Equations
  1. LogDC provides an output that is a logarithmic function of the input. If, for example, the scaling is 1 volt/decade, the output changes by 1V for any tenfold increase of the input.
    The intercept point is the input level at which the output voltage is 0.
    Vout = VoltSlope × log ((Vin / VoltIntercept) + 1)
  2. Several logarithmic amplifiers are available in ADS: LogACDemod, LogDC, LogSuccDetect, and LogTrue. LogACDemod, LogSuccDetect, and LogTrue accept an RF input and generate a DC output voltage proportional to the log of the input voltage. LogDC will accept an RF input but does not generate a DC output.
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