ahkab.switch¶

Implementation of a voltage controlled switch.

This module defines two classes: switch_device, switch_model

class switch_device(n1, n2, sn1, sn2, model, ic=None, part_id=u'S')[source]¶

This is a general switch element.

It has the following structure:

In ASCII for those who are consulting the documentation from the Python command line:

sn1 o--+         +--o n1
       |         |
      +-+      \ o
      |R|       \
      +-+        +
       |         |
sn2 o--+         +--o n2

The behavior is set by the model supplied.

The device instance calls the following methods in the model:

get_i(ports_v, device) - output current
get_go(ports_v, device) - ouput conductance
get_gm(ports_v, device) - output transconductance
get_dc_guess(self, is_on) - guesses for OP

The device instance accesses the following attributes: part_id (a string), the device label.

Parameters:

n1 : str: Positive output node (+)
n2 : str: Negative output node (-)
sn1 : str: Positive input node (+)
sn2 : str: Negative input node (-)
model : model obj: An instance of (v)switch_model
ic : bool, optional: The initial conditions: True stands for on, False for off.

Selected methods:

get_output_ports() -> (n1, n2)
get_drive_ports() -> (n1, n2), (ns1, ns2)

g(op_index, ports_v, port_index, time=0)[source]¶

Returns the differential (trans)conductance.

The transconductance is computed wrt the port specified by port_index when the element has the voltages specified in ports_v across its ports, at (simulation) time.

Parameters:

ports_v : list: Voltages applied to the switch. The list should be in the form: [voltage_across_port0, voltage_across_port1, ... ]
port_index : int: The index of the output port.
time : float: The simulation time at which the evaluation is performed. Set it to None during DC analysis.

Returns:

g : float: The transconductance.

get_drive_ports(op)[source]¶

Get the ports that drive the output ports.

Parameters:

op : op solution: The OP where the drive ports are used.

Returns:

pts : tuple of tuples of ports nodes, as: (port0, port1, port2 ... )

Where each port is in the form: port0 = (nplus, nminus)

get_netlist_elem_line(nodes_dict)[source]¶: Return a netlist line corresponding to the switch.

get_op_info(ports_v)[source]¶

Information regarding the Operating Point (OP)

Parameters:

ports_v : list of lists: The parameter is to be set to [[v]], where v is the voltage applied to the switch terminals.

Returns:

op_keys : list of strings: The labels corresponding to the numeric values in op_info.
op_info : list of floats: The values corresponding to op_keys.

get_output_ports()[source]¶

Get the output port.

The output port is (n1, n2) for the voltage-controlled switch case.

Returns:

pts : tuple of tuples of ports nodes: Such as: (port0, port1, port2 ... ). Where each port is in the form: port0 = (nplus, nminus)

get_value_function(identifier)[source]¶

i(op_index, ports_v, time=0)[source]¶

Returns the current flowing in the element.

The element is assumed to be biased with the voltages applied as specified in the ports_v vector.

Parameters:

op_index : int: The index of the output port for which the current is evaluated.
ports_v : tuple: A tuple constructed such as (voltage_across_port0, voltage_across_port1, ... )
time : float, optional: The simulation time at which the evaluation is performed. It is needed by time-variant elements, and it has no effect here. Set it to None during DC analysis.

Returns:

i : int: The output current.

update_status_dictionary(ports_v)[source]¶

Updates an internal dictionary that can then be used to provide information to the user regarding the status of the element.

Normally, one would call get_op_info().

Returns:

None.

class vswitch_model(name, VT=None, VH=None, VON=None, VOFF=None, RON=None, ROFF=None)[source]¶

Voltage-controlled switch model.

sn1 o--+         +--o n1
       |         |
      +-+      \ o
      |R|       \
      +-+        +
       |         |
sn2 o--+         +--o n2

Note that:

R is infinite.
The voltage needed to close the switch is: \(V(s_{n1})-V(s_{n2}) > V_T+V_H\).
To re-open it, one needs to satisfy the relationship: \(V(s_{n1})-V(s_{n2}) < V_T-V_H\).

The switch commutes between two statuses:

\(R_{OUT} = R_{OFF}\)
\(R_{OUT} = R_{ON}\)

None of which can be set to zero or infinite.

The switching characteristics are modeled with \(tanh(x)\).

get_dc_guess(is_on)[source]¶: Returns a list of two floats to be used as initial guesses for the OP analysis

get_gm(xxx_todo_changeme2, dev, debug=False)[source]¶: Returns the source to output transconductance or d(I)/d(Vsn1-Vsn2).

get_go(xxx_todo_changeme1, dev, debug=False)[source]¶: Returns the output conductance d(I)/d(Vn1-Vn2).

get_i(xxx_todo_changeme, dev, debug=False)[source]¶: Returns the output current.

print_model()[source]¶: All the internal parameters of the model get printed out, for visual inspection.