Question

For the circuit shown below, design the values of R1 and R2 that will cause Vout-6 Vif VIv-9 V. If the resistors you chose have a tolerance of 1 %, what is the maximum and minimum values of Vout? Design R3 so that the LED will be properly lit, if IF=10 mA, VF-3 V and Vout-6 V Design equations from the data sheet: VOUT-1.25%(1+R2 R1) U1 OUT ININLT OUT R3 R1 V1 (R3) R1) ADJ LT317A D1 IN) R2 (R2) NSCW100 Vout maximum Vout minimum The relative tolerance for this problem is 1 %

Answer 1

LM317 Design Calculation

Vout = 6V

Vin = 9V

Vout = Vref * (1 + -)

Say, R2=1KΩ = 1000Ω

Then,

6= 125. (1+1000)

Then, R1 = 263Ω

Therefore, with R1=263Ω and R2=1KΩ, We get Vout = 6V.

For LED to properly lit, and Vf=3V, If = 10 mamp,

The resistance R3 = R3= VI=6000 mV10 mamp=600Ω

6000 mr-600Ω R3 =-= mv I 10 mamp V