In reality a transistor is generally added to the circuit to provide enough power to control the relay, while a diode ... than sufficient in this case. Most NPN-type BJTs will work fine though.

[Kevin Darrah] wanted to make a simple 3.3V regulator without using an integrated circuit. He wound up using two common NPN transistors and 4 1K resistors. The circuit isn’t going to beat out a ...

This transistor switching circuit uses an npn transistor, a voltage divider (consisting of a \(5 kΩ \) resistor and thermistor) and a \(5 V\) power supply. Use the information in the table to ...