LDR VCA análisis

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Revisión del 22:51 10 ago 2026 de Antonio (discusión | contribs.) (Página creada con «Assumptions: * All of the opamps are ideal (A<sub>d</sub>=∞, A<sub>cm</sub>=0, I<sub>in</sub>=0). * The two LDRs are the same. * The two LDRs are exposed to the same amount of light from the LED. * The LDRs are shielded from ambient light. Because I<sub>in</sub>=0, all of the current from the control input continues through the bottom LDR, to the -15V supply. V<sub>control</sub> / 10k = 15 / R<sub>LDR</sub>, so <br> R<sub>LDR</sub> = (15 * 10k) / V<sub>control</s…»)
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Assumptions:

  • All of the opamps are ideal (Ad=∞, Acm=0, Iin=0).
  • The two LDRs are the same.
  • The two LDRs are exposed to the same amount of light from the LED.
  • The LDRs are shielded from ambient light.

Because Iin=0, all of the current from the control input continues through the bottom LDR, to the -15V supply.

Vcontrol / 10k = 15 / RLDR, so
RLDR = (15 * 10k) / Vcontrol
RLDR = 150k / Vcontrol (eq 1)

We assume the two LDRs have the same resistance at all times.

The audio path is composed of two gains, cascaded.

Av1: The voltage gain from the AUDIO INPUT terminal to the left terminal of the upper LDR.
Av2: The voltage gain from the left terminal of the upper LDR to the OUTPUT terminal, assuming the output is unloaded.

Av1 = -1 * 150k / 150k
Av1 = -1

Av2 = -1 * 150k / RLDR (eq 2)

Substituting the expression for RLDR from (eq 1) into (eq 2), we get:

Av2 = -150k / (150k / Vcontrol), or
Av2 = -Vcontrol

Therefore,

Atotal = Av1 * Av2
Atotal = -1 * -Vcontrol
Atotal = Vcontrol

Obtenido de «https://fab.uy/index.php?title=LDR_VCA_análisis&oldid=458»