Always bigger is better and there is nothing good a heat sink as large as possible. The dimensions of the heat sink are just approximate values and you can use slightly bigger or smaller ones according to the availability.MJ4502 requires a 6 x 6 x 2 cm Finned Aluminium type heat sink.LM195 also requires a similar heat sink.The heat sink can be a 2 x 2 x 2 cm Finned Aluminium type.A heat sink must be fitted to the LM317 in all applications where the output current exceeds 250mA.Maximum load current LM317 can handle is 1A.Any way a PCB is the better option if you can make it.All circuits shown above can be wired on perf board.LM195 is a monolithic power transistor with complete overload protection. In simple words the current limiting circuit replaces the “emitter resistance” of a classic transistor emitter follower. The circuit shown below is nothing but a emitter follower circuit using power transistor LM195 (Q6) with a current limiter circuit based on LM317 is connected at the emitter. The power follower circuit shown below can handle up to 600mA of output current. A typical voltage follower circuit designed using a small signal transistor can handle few hundreds milli amperes of current. A power follower is nothing but a voltage follower with high current capability. Power follower circuit using LM317.Ī voltage follower circuit is a circuit which produces considerable current gain while the voltage gain is maintained unity (or close to it). LED D2 provides a visual indication when the circuit is running in the constant current mode. POT R10 can be used to adjust the output current while POT R11 can be used to adjust the output voltage.

C6 is the input filter capacitor while C9 is the output filter capacitor. Resistor R16 limits the input current to the LM317 and base current to the transistor Q5. The output voltage of the regulator circuit is fed back to the non inverting input of the opamp while output voltage of the opamp is fed back to the inverting input of the opamp itself through capacitor C7. Diode D3 and capacitor C3 forms a compensation circuitry for the opamp. In addition to LM317, LM310 a single operational amplifier is also used in the circuit. Such a circuit is a very inevitable gadget on the work bench of an electronic enthusiast. The circuit shown above is of a 5A constant current / constant voltage regulator using LM317. 5A constant current constant voltage regulator.ĥA constant current constant voltage regulator Resistor R4 sets the maximum output voltage and it is according to the equation V out Max = 1.25V (1 + (R4/R3)) + (Iadj x R4). The width of each step depends on the value of the resistors you choose. Addition of each resistance in parallel to the R4 will reduce the effective resistance of the path and so the output voltage of the resistance will decrease in steps. Logic high at terminal A will make Q1 ON and so resistor R5 will be added parallel to R4 and so on. In simple words the output voltage will be according to the logic level of the digital inputs A, B, C and D.

Parallel to the resistor R4, four more resistor branches each with a transistor switch is added and these resistors can be included or excluded in to the circuit by making the corresponding switching transistor ON. The circuit is a just a modification of the ordinary voltage regulator using LM317. LM317 voltage regulator with digitally selected outputĪ very simple adjustable regulator circuit with digitally selected output is shown above. Adjustable regulator with digitally selected output. The output voltage of the regulator circuit depends on the equation, Vout = 1.25V (1 + (R2/R1)) + I adj R2. C1 is the input filter capacitor while C2 is the output filter capacitor. Resistor network comprising of R1 and R2 connected in association to the pin1 (adj) is used to set the output voltage. Input voltage is fed to the pin3 (v in) of the IC and regulated output voltage is available from pin 2 ( V out) of the IC. A classic voltage regulator circuit using LM317 is shown above.

Lm317 icircuit