A diode could also be shapely in SPICE by a diode statement in conjunction with a model statement. The diode statement specifies the diode name, the nodes to which the diode is connected, and its model name. The model incorporates an intensive range of diode characteristics like DC and small-signal behavior, temperature dependency, and noise generation. The model parameters take into consideration temperature effects, numerous capacitances, and physical properties of semiconductors.
The SPICE model for a reverse-biased diode is shown in Fig-1. The small-signal and static models that square measure generated by SPICE square measure shown in Fig- a pair of and 3, severally. within the static model, the diode current, that depends on its
SPICE small-signal diode model.
SPICE diode model with reverse-biased condition
voltage is delineated by a current supply. The small-signal parameters square measure generated by SPICE from the in operation purpose. SPICE generates a posh model for diodes. The model equations that square measure utilized by SPICE square measure represented in Refs. [1,2]. In several cases, particularly the amount at that this book is aimed, such complicated models aren’t necessary. several model parameters are often unnoticed by the users, and SPICE assigns default values to the parameters.
The name of a diode must start with D, and it takes the general form
Diode symbol and model parameters: where metal and NK are the anode node and therefore the cathode node, severally. this flows from anode node metal through the diode to cathode node NK. DNAME is the model name. The PSpice schematic of a diode with a model name Dbreak is shown in the image. The EVAL library of the PSpice student version supports few low-power diodes, like D1N4002, D1N4148, and D1N914. However, the user will amendment the model parameters of a D-break device. Click the correct push to open the window Edit PSpice Model as shown in Figure seven.4b. The model name may also be modified. The
The typical V–I characteristic of a diode is shown. The characteristic can be expressed by an equation known as the Schockley diode equation, given by
Is = leakage (or reverse saturation) current, typically in the range 10−6 to 10−20 A.
VD = diode voltage with anode positive with respect to cathode V.
ID = current through the diode, A.
n = empirical constant is known as the emission coefficient (or ideality factor),
whose value varies from 1 to 2.