Is it true that silicon rectifiers produce higher DC output voltage than selenium rectifiers for the same AC input?

Is it true that silicon rectifiers produce higher DC output voltage than selenium rectifiers for the same AC input?

• A. True
• B. False
• C. It depends
• D. Not applicable

Answer: (A)

The main idea here is the forward voltage drop across the rectifier. When AC is converted to DC, the voltage that actually makes it to the load is the peak of the input minus the voltage drop in the conducting path. Silicon rectifiers have a relatively low forward drop—about 0.7 V per conducting diode, so a full-bridge path drops around 1.4 V. Selenium rectifiers, by contrast, require a higher forward drop due to their material and construction, often around 1.0–1.5 V per cell, with even more loss in a bridge at typical currents. That extra drop reduces the DC output for the same AC input. With or without smoothing, lower rectifier losses mean a higher DC level, so silicon rectifiers yield a higher DC output than selenium rectifiers under the same input.

The main idea here is the forward voltage drop across the rectifier. When AC is converted to DC, the voltage that actually makes it to the load is the peak of the input minus the voltage drop in the conducting path. Silicon rectifiers have a relatively low forward drop—about 0.7 V per conducting diode, so a full-bridge path drops around 1.4 V. Selenium rectifiers, by contrast, require a higher forward drop due to their material and construction, often around 1.0–1.5 V per cell, with even more loss in a bridge at typical currents. That extra drop reduces the DC output for the same AC input. With or without smoothing, lower rectifier losses mean a higher DC level, so silicon rectifiers yield a higher DC output than selenium rectifiers under the same input.