Electronic – Driving LM317 with pwm signal

linear-regulatorpwm

I'm trying to drive a LM317T with a PWM signal coming from my Arduino UNO.
Here is my circuit:

schematic

simulate this circuit – Schematic created using CircuitLab

The PWM frequency is about 500Hz and I'm using a TLC2272 op amp and a LM317T regulator.
If the V_ref of the regulator is 1.25V, shouldn't I get an output voltage 1.25v greater than the adjust voltage?
When I measure V_out – V_adj I get about 2V.

What's wrong with my circuit?

Thanks

Best Answer

shouldn't I get an output voltage 1.25v greater than the adjust voltage? When I measure V_out - V_adj I get about 2V.

Yes, assuming other conditions of the circuit is satisfiedd.

What's wrong with my circuit?

Read the data sheet thoroughly. The circuit requires some minimum level of current to flow through for it to work.

Related Topic