Test: The Point Contact Diode - Electrical Engineering (EE) MCQ

The diode base of SnTe or Bi₂Te₃ is highly detection sensitive. They are mechanically stable over long periods of use either as harmonic generators or mixers. They are emphasized in the 2-200THz region.

The diode contains a die of a semiconductor material on which an epitaxial layer is deposited. It uses the metal whisker to make pressure contact against that layer. It has a low breakdown voltage.

The current flow of the point contact diode is not independent of voltage applied to the crystal unlikely to a general PN diode. This characteristic of contact diode makes its capacitance high at high frequency. A small capacitive current flows in the circuit.

 The barrier capacitance at the point is very low about 0.1pF to 1pF. The capacitance between the cat whisker and crystal is less compared to junction diode capacitance between both sides of the diode. For a general PN diode is 0.008µF to 20µF.

The operation of a contact diode depends on the pressure of contact between semiconductor crystal and point. The cat whisker wire presses against the crystal to form a section and the section allows the current flow. This is similar to the behaviour of PN diode.

The diode contains two sections having a small rectangular crystal of N type silicon and a fine beryllium-copper and bronze-phosphor. It has a tungsten wire which is called as a cat whisker wire. This helps in pressing one section to other.

The point contact diodes are the oldest microwave semiconductor devices. They were developed during world war 2. They have excessive applications in microwave fields and used as receivers and detectors.

It’s used in high frequency conversions and circuits in the order of 10KHz or above. The reactance due to capacitance is high and at high frequency a very small capacitive current flows.

The behaviour of a contact diode is similar to that of a PN diode. It has a tungsten wire which is called as a cat whisker wire. This helps in pressing one section to other.

The current flow of the point contact diode is not independent of voltage applied to the crystal unlikely to a general PN diode. A small capacitive current flows in the circuit.