.. include:: /project-links.txt
.. include:: /abbreviation.txt


############################
 Zener Characteristic Curve
############################

.. getthecode:: zener-characteristic-curve.py
    :language: python3
    :hidden:

This example shows how to simulate and plot the characteristic curve of a Zener diode.

.. code-block:: py3

    
    
    import numpy as np
    import matplotlib.pyplot as plt
    
    
    import PySpice.Logging.Logging as Logging
    logger = Logging.setup_logging()
    
    
    from PySpice.Doc.ExampleTools import find_libraries
    from PySpice.Spice.Netlist import Circuit
    from PySpice.Spice.Library import SpiceLibrary
    from PySpice.Unit import *
    
    
    libraries_path = find_libraries()
    spice_library = SpiceLibrary(libraries_path)
    
    


.. image:: zener-diode-characteristic-curve-circuit.png
    :align: center


.. code-block:: py3

    
    circuit = Circuit('Diode DC Curve')
    
    circuit.include(spice_library['1N4148'])
    # 1N5919B: 5.6 V, 3.0 W Zener Diode Voltage Regulator
    circuit.include(spice_library['d1n5919brl'])
    
    circuit.V('input', 'in', circuit.gnd, 10@u_V)
    circuit.R(1, 'in', 'out', 1@u_Ω) # not required for simulation
    # circuit.X('D1', '1N4148', 'out', circuit.gnd)
    circuit.X('DZ1', 'd1n5919brl', 'out', circuit.gnd)
    
    simulator = circuit.simulator(temperature=25, nominal_temperature=25)
    analysis = simulator.dc(Vinput=slice(-10, 2, .05)) # 10mV
    
    figure = plt.figure(1, (20, 10))
    
    zener_part = analysis.out <= -5.4@u_V
    # compute derivate
    # fit linear part
    
    axe = plt.subplot(121)
    axe.grid()
    # Fixme: scale
    axe.plot(analysis.out, -analysis.Vinput*1000)
    axe.axvline(x=0, color='black')
    axe.axvline(x=-5.6, color='red')
    axe.axvline(x=1, color='red')
    axe.legend(('Diode curve',), loc=(.1,.8))
    axe.set_xlabel('Voltage [V]')
    axe.set_ylabel('Current [mA]')
    
    axe = plt.subplot(122)
    axe.grid()
    # Fixme:
    # U = RI   R = U/I
    dynamic_resistance = np.diff(-analysis.out) / np.diff(analysis.Vinput)
    # axe.plot(analysis.out[:-1], dynamic_resistance/1000)
    axe.semilogy(analysis.out[10:-1], dynamic_resistance[10:], basey=10)
    axe.axvline(x=0, color='black')
    axe.axvline(x=-5.6, color='red')
    axe.legend(('Dynamic Resistance',), loc=(.1,.8))
    axe.set_xlabel('Voltage [V]')
    axe.set_ylabel('Dynamic Resistance [Ohm]')
    
    # coefficients = np.polyfit(analysis.out[zener_part], dynamic_resistance[zener_part], deg=1)
    # x = np.array((min(analysis.out[zener_part]), max(analysis.out[zener_part])))
    # y = coefficients[0]*x + coefficients[1]
    # axe.semilogy(x, y, 'red')
    
    plt.tight_layout()
    plt.show()
    


.. image:: zener-characteristic-curve.png
    :align: center