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LogSuccDetect (Successive Detection Logarithmic Amplifier

Symbol

Available in ADS

Parameters

Name

Description

Units

Default

NumStages

Number of stages

None

5

StageGain

Gain per stage

dB

10

CurrentSlope

Gradient of transfer characteristic

A/decade

1.e-3

Z1

Reference impedance for port 1

Ohm

50

Notes/Equations
  1. This amplifier use a successive detection scheme to provide an output current proportional to the logarithm of the input voltage. The amplifier consists of several amplifier/limiter stages (NumStages specifies how many), each having a small signal gain (StageGain specifies the gain). Each stage has an associated full-wave detector, whose output current depends on the absolute value of its input stage. These output currents are summed to provide the output scaled at the CurrentSlope (amp/decade). The output contains amplitude information only, regardless of any phase information. A simplified block diagram of this component is shown in Simplified Block Diagram of a 5-Stage LogSuccDetect.

    Simplified Block Diagram of a 5-Stage LogSuccDetect
  2. Several logarithmic amplifiers are available in ADS: LogACDemod, LogDC, LogSuccDetect, and LogTrue. These components accept an RF input and generate a DC output voltage proportional to the log of the input voltage.
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