If your introduction to digital electronics came more years ago than you’d care to mention, the chances are you did so with 5V TTL ... on this circuit that use diodes instead of a resistor ...

In In this installment of Circuit VR, I’m looking inside practical ... In theory, the transistor is either off so you basically have a 5V pullup resistor to the output, or it is in saturation ...

Using properties of a series circuit, the sum of the voltages across the LED and resistor R must equal the supply voltage. \({V_s} = {V_{LED}} + {V_R}\) Now substitute the supply voltage (\(6V ...