Diferencia entre revisiones de «LDR VCA análisis»
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: | Assumptions: | ||
* | * Los dos opamps son ideales (A<sub>d</sub>=∞, A<sub>cm</sub>=0, I<sub>in</sub>=0). | ||
* | * Los dos LDRs son iguales. | ||
* | * Los dos LDRs están expuestos a la misma cantidad de luz desde el LED. | ||
* | * Los LDRs están escondidos de la luz ambiente. | ||
Because I<sub>in</sub>=0, all of the current from the control input continues through the bottom LDR, to the -15V supply. | Because I<sub>in</sub>=0, all of the current from the control input continues through the bottom LDR, to the -15V supply. | ||
Revisión del 22:54 10 ago 2026
Assumptions:
- Los dos opamps son ideales (Ad=∞, Acm=0, Iin=0).
- Los dos LDRs son iguales.
- Los dos LDRs están expuestos a la misma cantidad de luz desde el LED.
- Los LDRs están escondidos de la luz ambiente.
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