mirror current amplitude modulation

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Mojo Pin__

Joined Apr 13, 2019
83
The oscilloscope traces below are taken from a 2 mosfet mirror current circuit with a light dependant resistor as the load. Can someone help me understand why the yellow signal is not enveloping the AM signal? Is it to do with the latency of the LDR? Also, to me the Amplitude of the green wave doesn't look like it changes although I have been told that this is a form of amplitude modulation.

The only other thing I could think of was maybe some kind of internal capacitance in the MOSFETs was causing the shift up and down?

I'd really like to understand this

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crutschow

Joined Mar 14, 2008
27,198
I have been told that this is a form of amplitude modulation.
Whoever told you that is wrong.
That's not amplitude modulation, it's just a low frequency wave riding on (added to) a high frequency wave.
Notice below how the high frequency signal changes amplitude in sync with the signal, while your signal just goes up and down but doesn't actually change the high frequency pp amplitude.

As to why, your circuit is not modulating, post your schematic.

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