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).
The entire 1N40xx series of power diodes are all silicon. The OA79 small signal diode is germanium.
0a79 ( germanium diode )in glass construction form is used in AM detector circuits.
Germanium
About 0.2V
The symbol 'A' indicates that this device is made from germanium . as you may know germanium has less cut in voltage so this device is used for low power signal or for signal processing. also the leakage current or reverse saturation current of germanium is greater than silicon.
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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
In general O in diodes stands for germanium.since OA79 is a germanium diode O stands for germanium
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.
In OA79, the letter A stands for rectifier diode and O stands for Germanium. It acts as a point contact germanium diode and also be replaced with 1N4148 depending on the circuit.
The entire 1N40xx series of power diodes are all silicon. The OA79 small signal diode is germanium.
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.
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0a79 ( germanium diode )in glass construction form is used in AM detector circuits.
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.
IN IN = 1N: Refers to the number of junctions (1N= 1 junction). O= Germanium, A= rectifier diode, so OA = germanium rectifier diode.