|
Log Amplifier
A log amplifier, which may spell ''log'' as ''logarithmic'' or ''logarithm'' and which may abbreviate ''amplifier'' as ''amp'' or be termed as a ''converter'', is an electronic amplifier that for some range of input voltage V_\text has an output voltage V_\text approximately proportional to the logarithm of the input: :V_\text \approx K \cdot \ln \left(\frac\right) \, , where V_\text is a normalization constant in volts, ''K'' is a scale factor, and ''\ln'' is the natural logarithm. Some log amps may mirror negative input with positive input (even though the mathematical log function is only defined for positive numbers), and some may use electric current as input instead of voltage. Log amplifier circuits designed with operational amplifiers (opamps) use the exponential current–voltage relationship of a p–n junction (either from a diode or bipolar junction transistor) as negative feedback to compute the logarithm. Multistage log amplifiers instead cascade multiple simple ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
True RMS Converter
For the measurement of an alternating current the signal is often converted into a direct current of equivalent value, the root mean square (RMS). Simple instrumentation and signal converters carry out this conversion by filtering the signal into an average rectified value and applying a correction factor. The value of the correction factor applied is only correct if the input signal is sinusoidal. True RMS provides a more correct value that is proportional to the square root of the average of the square of the curve, and not to the average of the absolute value. For any given waveform, the ratio of these two averages is constant and, as most measurements are made on what are (nominally) sine waves, the correction factor assumes this waveform; but any distortion or offsets will lead to errors. To achieve this, a ''true RMS converter'' requires a more complex circuit. Digital RMS converters If a waveform has been digitized, the correct RMS value may be calculated directly. Most ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
