• The 1N914 diode at the far right is a germanium rectifier diode.tech parts image by naolin from Fotolia.com
  
  While most diodes are constructed of silicon, there are some instances where a germanium diode may be preferred. For example, germanium diodes require a smaller operating forward voltage than silicon diodes require. Germanium diodes are also capable of enduring higher operating temperatures than similar silicon diodes can handle. One specific germanium diode, the 1N914, is used in high-speed electronic circuits. These high-voltage, low-current diodes are often used in rectifier circuits.
  
  

Forward Voltage

• One of the key differences between a germanium rectifier and a silicon rectifier diode is the voltage needed to allow the diode to conduct electrical current. Typical silicon diodes, such as a 1N4001 diode, require approximately 0.7 volts across the diode to allow electrical current to begin flowing between the anode and the cathode. The germanium-construction 1N914 requires 0.62 volts to allow electrical current to flow through the diode.
  
  

Reverse Voltage

• Ideally, when a diode has a larger voltage at the cathode than at the anode, the diode acts as a one-way check valve, disallowing electrical current to flow through the diode. In practice, however, a diode allows a very small current (less than one milliamp) to flow through the diode in this condition. If the voltage differential gets large enough, the diode will begin to break down, and current will flow through the diode until the diode is damaged or destroyed.
  
  The voltage at which the diode begins to break down is referred to as the "reverse voltage" value. Germanium diodes, such as the 1N914, are hardy when compared to silicon diodes. While a silicon-construction 1N4001 diode will begin to break down at 50 volts, the reverse voltage value of a germanium-construction 1N914 is 75 volts.
  
  

Operating Temperature Limitations

• A 1N914 diode may be used in environments that range in temperature from -65 degrees Celsius to 200 C. This is a greater temperature range than a silicon-construction 1N4001 diode can endure, -55 C to 175 C.