There is no exact substitute for a germanium diode, except another germanium diode. However if the only concern is to get a lower forward voltage drop than that of a silicon diode (0.7V), then a schottky barrier diode may be a suitable replacement as its forward voltage drop (<0.1V) is even lower than that of a germanium diode (0.2V).
About 0.2V
The significant operational difference between a Si diode and a Ge diode is that Si diodes have a knee voltage of 0.7V needed to allow current flow and Ge diodes have an operational voltage of 0.3V to allow current flow.
A; The 1N4xxx series of rectifier diodes are specified as 1 amp forward conduction. the last number signify the maxi mun reverse voltage it can sustain without breakdown.
The point in the forward operating region of the characteristic curve where conduction starts to increase rapidly is called Knee voltage of a PN Junction Diode.The breakdown voltage of a diode is the minimum reverse voltage to make the diode conduct in reverse.(or) Breakdown voltage is a parameter of a diode that defines the largest reverse voltage that can be applied without causing an exponential increase in the current in the diode.-- Dinakar
Silicon = 0.7v : Germanium = 0.3v
There is no exact substitute for a germanium diode, except another germanium diode. However if the only concern is to get a lower forward voltage drop than that of a silicon diode (0.7V), then a schottky barrier diode may be a suitable replacement as its forward voltage drop (<0.1V) is even lower than that of a germanium diode (0.2V).
A silicon diode has a voltage drop of approximately 0.7V, while a germanium diode has a voltage drop of approximately 0.3V. Though germanium diodes are better in the area of forward voltage drop, silicon diodes are cheaper to produce and have higher breakdown voltages and current capabilities.
A Germanium diode has a much lower breakdown voltage than a silicone diode.
silicon diode is preferred more when compared with germanium diode because in silicon diode the operating voltage is 0.7v where as in germanium diode the operating voltage is 0.3v , germanium is temperature sensitive so it can be easily destroyed by increasing temperature hence silicon diode is preferred more
About 0.2V
That is the property of that material.
The silicon diode (unless its a Schottky diode) conducts at approximately 0.6 volts. The germanium diode, however, conducts at a much lower voltage, typically 0.2 volts. This means that the germanium diode is better at small signal rectification applications, such as AM radio detectors, allowing a smaller tuner tank circuit.
The barrier voltage of a diode is 0.7v for silicon and 0.3 for germanium. after this voltage is reached the current starts increasing rapidly... till this voltage is reached the current increases in very small steps...
To forward bias a germanium diode you need to reach between 0.2 and 0.3 V between anode (+) and cathode (-). Once this voltage is reached, the diode will conduct. Make sure you have a resistor to limit the forward current to a safe (for the diode, that is) value.
Cut in voltage (Knee voltage): The forward voltage at which the current through the P-N Junction starts increasing rapidly is called as Cut in voltage or knee voltage.
The significant operational difference between a Si diode and a Ge diode is that Si diodes have a knee voltage of 0.7V needed to allow current flow and Ge diodes have an operational voltage of 0.3V to allow current flow.