Resonant Tunnelling Transistor Demo Instructions


The demo program contains the following items:

	1. The circuit diagram of the bistable pair.
	2. The load and driver output curves.
	3. The Contacts Menu.
	4. The Curves Menu.
	5. The Apply Button.
	6. The Run Button and the run-time output plot.


1. The circuit diagram of the bistable pair

This diagram initially consists of a pair of resonant tunnelling diodes (RTDs) connected in series. The voltage source Vclock is applied to the load RTD, and the driver RTD is connected to ground. The output voltage of the bistable pair is taken from the node between the load and driver devices. Up to 4 base contacts can be added to each of the load and the driver devices, effectively turning them into resonant tunnelling transistors. These base contacts will be shown on the circuit diagram as they are added.

2. The load and driver output curves

These curves display the current-voltage output characteristics of both the load and the driver devices. It is important to note that the curves show the operating characteristics of each of the devices in isolation with the entire clock voltage being swept across them. If the maximum current value (y-axis), peak clock voltage (x-axis) or any of the inputs to the base contacts are altered, the device output curves will be effected. However, these effects will only take place once the Apply button has been pressed.

3. The Contacts Menu

This menu allows base contacts to be added or removed from the load and driver devices. Each of the devices can have a maximum of 4 base contacts, and a minimum of none. An input to a base contact is expressed in volts, and is initially zero. A unit change to a base input (1 unit = 1 volt) corresponds to a unit change in the peak height (1 unit = 1mA) of the resonant tunnelling device to which it is connected. For example, the load device initially has a peak height of 5mA. Applying a total base voltage of 10V to the load will cause an increase in peak height of 10mA, giving a peak height of 15mA. Note that changes in the peak height will not take effect until the Apply Button has been pressed.

4. The Curves Menu

This menu allows the user to alter the device output curves in the following ways: a. Zero load peak. The current peak height of the load device when it has a total base input voltage of zero (or alternatively, no base contacts). The initial value is 5mA. b. Zero driver peak. Ditto for the driver device, although the initial value is 10mA. c. Max current. The maximum current value permitted to be plotted along the y-axis. The inital value is 15mA. d. Clock voltage. The final value reached by the clock voltage when it finishes its sweep. Also the maximum value along the x-axis. The initial value is 1.5V. Again, changes to any of these values will not take effect until the Apply Button has been pressed.

5. The Apply Button

Any changes made using the menu options, or any changes in base input, will not take effect until this button has been pressed.

6. The Run Button and the run-time output plot

Pressing the Run Button (at the bottom of the demo program window) will begin to sweep the clock voltage across the bistable pair from 0 to the maximum set by the user (or 1.5V by default). The output voltage corresponds to the intersection of the load and the driver curves, and is plotted within the run-time output plot beneath the circuit diagram. The simulation will come to an end once the clock voltage has reached its maximum. The final output voltage is displayed, along with the resulting output state. State 0 is reached if the load curve is lower than the driver, and state 1 is reached if it is higher.

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Last updated: July 24, 1996 by Colin Moffat