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



.. getthecode:: transistor.py
    :language: python3
    :hidden:
    :notebook:

====================
 Bipolar Transistor
====================
This example shows how to simulate the characteristic curves of a bipolar transistor.

.. code-block:: py3

    
    # Fixme: Complete
    
    
    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.Probe.Plot import plot
    from PySpice.Spice.Library import SpiceLibrary
    from PySpice.Spice.Netlist import Circuit
    from PySpice.Unit import *
    
    
    libraries_path = find_libraries()
    spice_library = SpiceLibrary(libraries_path)
    
    
    figure, ((ax1, ax2), (ax3, ax4)) = plt.subplots(2, 2, figsize=(20, 10))
    
    

We define a basic circuit to drive an NPN transistor (2n2222a) using two voltage sources.

.. image:: transistor.png
    :align: center


.. code-block:: py3

    
    circuit = Circuit('Transistor')
    
    Vbase = circuit.V('base', '1', circuit.gnd, 1@u_V)
    circuit.R('base', 1, 'base', 1@u_kΩ)
    Vcollector = circuit.V('collector', '2', circuit.gnd, 0@u_V)
    circuit.R('collector', 2, 'collector', 1@u_kΩ)
    # circuit.BJT(1, 'collector', 'base', circuit.gnd, model='generic')
    # circuit.model('generic', 'npn')
    circuit.include(spice_library['2n2222a'])
    circuit.BJT(1, 'collector', 'base', circuit.gnd, model='2n2222a')
    

We plot the base-emitter diode curve :math:`Ib = f(Vbe)` using a DC sweep simulation.

.. code-block:: py3

    
    simulator = circuit.simulator(temperature=25, nominal_temperature=25)
    analysis = simulator.dc(Vbase=slice(0, 3, .01))
    
    ax1.plot(analysis.base, u_mA(-analysis.Vbase)) # Fixme: I_Vbase
    ax1.axvline(x=.65, color='red')
    ax1.legend(('Base-Emitter Diode curve',), loc=(.1,.8))
    ax1.grid()
    ax1.set_xlabel('Vbe [V]')
    ax1.set_ylabel('Ib [mA]')
    
    

We will now replace the base's voltage source by a current source in the previous circuit.

.. code-block:: py3

    
    circuit = Circuit('Transistor')
    Ibase = circuit.I('base', circuit.gnd, 'base', 10@u_uA) # take care to the orientation
    Vcollector = circuit.V('collector', 'collector', circuit.gnd, 5)
    # circuit.BJT(1, 'collector', 'base', circuit.gnd, model='generic')
    # circuit.model('generic', 'npn')
    circuit.include(spice_library['2n2222a'])
    circuit.BJT(1, 'collector', 'base', circuit.gnd, model='2n2222a')
    
    # Fixme: ngspice doesn't support multi-sweep ???
    #   it works in interactive mode
    
    
    ax2.grid()
    # ax2.legend(('Ic(Vce, Ib)',), loc=(.5,.5))
    ax2.set_xlabel('Vce [V]')
    ax2.set_ylabel('Ic [mA]')
    ax2.axvline(x=.2, color='red')
    
    ax3.grid()
    # ax3.legend(('beta(Vce)',), loc=(.5,.5))
    ax3.set_xlabel('Vce [V]')
    ax3.set_ylabel('beta')
    ax3.axvline(x=.2, color='red')
    
    for base_current in np.arange(0, 100, 10):
        base_current = base_current@u_uA
        Ibase.dc_value = base_current
        simulator = circuit.simulator(temperature=25, nominal_temperature=25)
        analysis = simulator.dc(Vcollector=slice(0, 5, .01))
        # add ib as text, linear and saturate region
        # Plot Ic = f(Vce)
        ax2.plot(analysis.collector, u_mA(-analysis.Vcollector))
        # Plot β = Ic / Ib = f(Vce)
        ax3.plot(analysis.collector, -analysis.Vcollector/float(base_current))
        # trans-resistance U = RI   R = U / I = Vce / Ie
        # ax3.plot(analysis.collector, analysis.sweep/(float(base_current)-analysis.Vcollector))
        # Fixme: sweep is not so explicit
    

Let plot :math:`Ic = f(Ib)`

.. code-block:: py3

    
    ax4.grid()
    ax4.set_xlabel('Ib [uA]')
    ax4.set_ylabel('Ic [mA]')
    
    simulator = circuit.simulator(temperature=25, nominal_temperature=25)
    analysis = simulator.dc(Ibase=slice(0, 100e-6, 10e-6))
    # Fixme: sweep
    ax4.plot(analysis.sweep*1e6, u_mA(-analysis.Vcollector), 'o-')
    ax4.legend(('Ic(Ib)',), loc=(.1,.8))
    
    
    plt.tight_layout()
    plt.show()
    


.. image:: transistor-plot.png
    :align: center