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Basic principles of amplifier

Edit: Guangzhou Langyuan Audio Equipment Co.Ltd      Date:Jun 17, 2016

Lock-in amplifier is in fact a analogue Fourier transform, and lock-in amplifier output is a DC voltage, which is proportional to the input signal of a specific frequency (parameter input frequency) signal amplitude. Other frequency components of the input signal to the output voltages will not be able to contribute.

Two sinusoidal signals, frequency is 1Hz, with a 90-degree phase difference result obtained by multiplying the multiplier is a sinusoidal signal with DC offset.

If it is a 1Hz and a 1.1Hz signal is multiplied by results obtained by multiplying the multiplier is the outline for a sinusoidal modulation, DC offset is 0.

Only fully consistent with reference signal frequency of the signal to be DC offset at the output multipliers, other signals at the output is AC signal. If you added a low-pass filter at the output of the multiplier, then all of the AC signal components are filtered out, leaving the DC component is proportional to the input signal of a specific frequency component in the signal amplitude.


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