LM 317 Regulater as a constant current source Experiment Procedure, Observations & Calculations, Result, Viva 2023

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Aim :

To construct an adjustable current source using LM 317, determine the limit of its output current and study the variation in output current with load.

Apparatus :

Unregulated power supply, IC LM 317, two resistance boxes, DC ammeter , DMM etc.

LM 317 Regulater constant current source - Experiment

 

Formula :

LM 317 Regulater constant current source - Experiment

 

Circuit Diagram :

LM 317 Regulater constant current source - Experiment

 

Procedure :

Credit : Ludic Science

  1. Switch on unregulated DC power supply and measure the input voltage Vin.
  2. Design the variable current source capable of sorcing a continuous current Io of 25 mA to 125mA. Using the relation,R1 = ,calculate R1 for suitable value of Io= 25 mA.
  3. Make necessary connection. Measure the minimum and maximum values of Io and compare it with expected values.
  4. For Io =  100 mA, connect the load resistance RL between adjust pin and ground. By increasing values of RL from zero in suitable steps, measure IL, VL for each value of RL.  
  5. Plot IL against VL and VL against RL graphs.
  6. Hence determine the maximum value of RL up to which the circuit function as a constant current source.
  7. Repeat the experiment for a different value of Io.

Observations :

 

Viva Question and Answers [FAQ] :

1. What is Regulater?

Ans : Any electrical or electronic device that maintains the voltage of a power source within acceptable limits.

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