mjcox2000 wrote:Since no one has posted a question yet:

An LED with voltage drop and internal resistance is in series with a voltage and resistance . The LED’s maximum rated current is , and the minimum current at which its light is visible is .

1. What is the minimum series voltage for the LED to emit visible light?
2. Given the value of , write equations for the minimum and maximum value of for the LED to emit visible light without burning out.

Voltage = [math]10^-^4 (R+2)+3.2[/math] Volts
Min R = [math][(V-3.2)/10^-^2]-2[/math] Ohms
Max R = [math][(V-3.2)/10^-^4]-2[/math] Ohms

mjcox2000 wrote:Since no one has posted a question yet:

An LED with voltage drop and internal resistance is in series with a voltage and resistance . The LED’s maximum rated current is , and the minimum current at which its light is visible is .

1. What is the minimum series voltage for the LED to emit visible light?
2. Given the value of , write equations for the minimum and maximum value of for the LED to emit visible light without burning out.

Voltage = [math]10^-^4 (R+2)+3.2[/math] Volts
Min R = [math][(V-3.2)/10^-^2]-2[/math] Ohms
Max R = [math][(V-3.2)/10^-^4]-2[/math] Ohms

Looks good. Your turn!

MIT ‘23
TJHSST ‘19
Longfellow MS

See my user page for nationals medals and event supervising experience.

The 0 current condition requires that [math]\frac{R_3}{R_4}=\frac{20}{280}[/math], and the 83.3mA current condition requires that the total parallel resistance be [math]180\Omega[/math], so [math]R_3+R_4=450\Omega[/math], so [math]\boxed{R_3=30\Omega,\ R_4=420\Omega}[/math].

MIT ‘23
TJHSST ‘19
Longfellow MS

See my user page for nationals medals and event supervising experience.

The 0 current condition requires that [math]\frac{R_3}{R_4}=\frac{20}{280}[/math], and the 83.3mA current condition requires that the total parallel resistance be [math]180\Omega[/math], so [math]R_3+R_4=450\Omega[/math], so [math]\boxed{R_3=30\Omega,\ R_4=420\Omega}[/math].

Given this orientation of an operational amplifier, find the value of Rf (in kΩ) if the Vin = 20 mV, Rg = 3.8 kΩ, and Vout = 64 mV
(sorry for my bad drawing, haha)

krasabnk wrote:
Given this orientation of an operational amplifier, find the value of Rf in kΩ if the Vin = 20 mV, Rg = 3.8 kΩ, and Vout = 64 mV
(sorry for my bad drawing, haha)