With a given AC input voltage, which rectifiers produce a higher DC output voltage than selenium rectifiers?

With a given AC input voltage, which rectifiers produce a higher DC output voltage than selenium rectifiers?

• A. Selenium; Silicon
• B. Germanium; Silicon
• C. Silicon; Selenium
• D. Carbon; Silicon

Answer: (C)

When you fix the AC input and look at the DC output after rectification, the voltage you get is the peak of the input minus the forward voltage drop of the rectifying elements. Selenium rectifiers have a relatively high forward drop, so they waste more of the peak voltage. Silicon rectifiers have a lower forward drop (about 0.7 V per diode, so a typical bridge loses roughly 1.4 V total), which means more of the input peak appears as DC across the load. That higher usable voltage is why silicon rectifiers produce a higher DC output than selenium rectifiers for the same AC input. Carbon and other materials aren’t typically used for this context, and germanium would also give a higher output due to its even lower drop, though it isn’t the pairing shown here.

When you fix the AC input and look at the DC output after rectification, the voltage you get is the peak of the input minus the forward voltage drop of the rectifying elements. Selenium rectifiers have a relatively high forward drop, so they waste more of the peak voltage. Silicon rectifiers have a lower forward drop (about 0.7 V per diode, so a typical bridge loses roughly 1.4 V total), which means more of the input peak appears as DC across the load. That higher usable voltage is why silicon rectifiers produce a higher DC output than selenium rectifiers for the same AC input. Carbon and other materials aren’t typically used for this context, and germanium would also give a higher output due to its even lower drop, though it isn’t the pairing shown here.