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Tunnel diodes: Difference between revisions
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Tunnel diodes are used in various circuits in Tektronix gear made from the early | '''Tunnel diodes (Esaki diodes)''' are used in various circuits in Tektronix gear made from the early 1960s until the 1980s. | ||
== Applications == | == Applications == | ||
Tunnel diodes were used where it was | Tunnel diodes were used where it was desirable to have fast and clean switching between two states. | ||
desirable to have fast and clean switching between two states. | |||
They were used in | They were used in | ||
* trigger circuits as Schmitt triggers, | * trigger circuits as Schmitt triggers, | ||
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== Relevant Distinguishing Parameters == | == Relevant Distinguishing Parameters == | ||
Many different types of tunnel diodes were made. The primary parameter that describes one is the peak current, which is the current at the top of the hill in the I-V curve. The other two relevant electrical parameters are the capacitance of the diode and whether it is made of GaAs or Ge. In some circuits, | Many different types of tunnel diodes were made. The primary parameter that describes one is the peak current, which is the current at the top of the hill in the I-V curve. The other two relevant electrical parameters are the capacitance of the diode and whether it is made of GaAs or Ge. In some circuits, another model of tunnel diode can be substituted with only minor modifications to the surrounding circuit. [[Stan Griffiths]] describes such a modification here: | ||
another model of tunnel diode can be substituted with only minor modifications to the surrounding circuit. [[Stan Griffiths]] describes such a modification here: | |||
* [[Tunnel Diode Replacement and Modification]] | * [[Tunnel Diode Replacement and Modification]] | ||
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(Alternatively and equivalently, it can be modeled as nonlinear resistance. However, the nonlinear VCCS model might be preferable because it avoids | (Alternatively and equivalently, it can be modeled as nonlinear resistance. However, the nonlinear VCCS model might be preferable because it avoids | ||
the confusing notion of negative resistance.) | the confusing notion of negative resistance.) | ||
Consider a tunnel diode biased by a DC current source that is slowly brought up from zero to a current just a few microamperes less than the diode's peak current. | Consider a tunnel diode biased by a DC current source that is slowly brought up from zero to a current just a few microamperes less than the diode's peak current. | ||
The quiescent voltage will be just less than the peak voltage. | The quiescent voltage will be just less than the peak voltage. | ||
Note that the I-V curve is nearly horizontal at this point, and therefore the incremental resistance of the diode is very high at this point. | Note that the I-V curve is nearly horizontal at this point, and therefore the incremental resistance of the diode is very high at this point. | ||
For simplicity, we can assume that the incremental resistance is infinite at this quiescent point. | For simplicity, we can assume that the incremental resistance is infinite at this quiescent point. | ||