Let me preface this by saying that I have zero background with electronics beyond plugging 7400-series chips into breadboards a decade ago, and earlier as a child.
I've been playing around with LM317s to power stuff via USB (5 volts), and wanted to get fancy and teach myself the basics of BJTs with the attached circuit. The idea was to use the LED to show that the LM317 was working. Since the target voltage is only 2 volts, that wouldn't be enough to drive the LED directly with a current-limiting resistor, as the LEDs I have need around 2.3 volts. It seemed like a great time to try out my first BJT circuit.
The circuit actually does work...but only if there's nothing attached to Vout. Once the intended load—a pair of headphones that actually does expect 2 volts—is attached, the voltage quickly drops under 1 volt before it shuts off. Regardless of the load, the LED stays on just fine.
I did make the canonical LM317 circuit previously and have been using it for probably a year to power the same headphones without issue, so something must be something up with the design of this circuit. Any ideas?
I don't have my heart set on making this work if it's silly or simply won't work, but I would like to learn where I went wrong so I can correct any of my own misconceptions. Thank you.
I've been playing around with LM317s to power stuff via USB (5 volts), and wanted to get fancy and teach myself the basics of BJTs with the attached circuit. The idea was to use the LED to show that the LM317 was working. Since the target voltage is only 2 volts, that wouldn't be enough to drive the LED directly with a current-limiting resistor, as the LEDs I have need around 2.3 volts. It seemed like a great time to try out my first BJT circuit.
The circuit actually does work...but only if there's nothing attached to Vout. Once the intended load—a pair of headphones that actually does expect 2 volts—is attached, the voltage quickly drops under 1 volt before it shuts off. Regardless of the load, the LED stays on just fine.
I did make the canonical LM317 circuit previously and have been using it for probably a year to power the same headphones without issue, so something must be something up with the design of this circuit. Any ideas?
I don't have my heart set on making this work if it's silly or simply won't work, but I would like to learn where I went wrong so I can correct any of my own misconceptions. Thank you.
