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.

[UCL Physics & Astronomy Homepage]
[UCL Image Processing Group Homepage]
Last updated: July 24, 1996 by Colin Moffat