The diode simulation circuit model
Technical field
The present invention relates to the semiconductor design technology, particularly a kind of diode simulation circuit model.
Background technology
The HSPICE emulator is acknowledged as " golden standard " in accurate circuit simulation field, and can provide the MOS device model that authenticated through foundries emulation by first-class emulation and analytical algorithm, is one of fastest, the circuit emulator of being trusted most.
In the HSPICE emulator of current semiconductor design owner stream, it is as follows that the electric current of conventional diode (diode) device simulation model is described formula:
Diode forward working current id is:
Formula 1;
Diode reverse breakdown current i d1 is:
Formula 2;
In formula 1 and the formula 2, ISeff is the watt current coefficient, and Vd is extraneous bias voltage, and N is the correction factor of current index item, and Vt is physical constant, and Bveff is the voltage breakdown of diode.
Can find out from formula 1 and formula 2, all adopt identical correction factor " N " when describing the exponential term of the forward current of diode and reverse breakdown current in the emulator, this is that a kind of model formation of more satisfactoryization is described.But in the actual conditions, Zener diode (zener diode) for example, the i-v curve that test obtains as shown in Figure 1, what the figure dotted line represented is the diode current voltage curve that actual measurement obtains, and the solid line representative is the i-v curve that model emulation obtains, wherein the x axle is diode two ends scanning voltages, and the y axle is measuring current, and scale is Log (A).Figure irises out in the left side part and is reverse breakdown current models fitting part, the right side is irised out part and is forward current models fitting part, can see the limitation owing to model formation in the emulator, model can't be aligned in both sides electric current slope under the logarithmic coordinate simultaneously, we can see that the left side breakdown current sharply rises with reverse voltage, the right side forward current increases with forward voltage, but about two slope of a curves be different, the slope of breakdown current more " precipitous " is a little.When models fitting, because the restriction of formula supposes that the Iseff value is fixing, model can only be adjusted by parameter " N " both slopes, and the result certainly will be for causing the sacrifice of some precision.
Summary of the invention
The technical problem to be solved in the present invention provides a kind of diode simulation circuit model, has improved model accuracy and the dirigibility of diode reverse characteristic, can both obtain preferably alignment precision at forward working current and the reverse breakdown current of diode.
For solving the problems of the technologies described above, diode simulation circuit model of the present invention comprises a forward diode model, also comprises a Voltage-controlled Current Source, a dead resistance;
Described Voltage-controlled Current Source is serially connected between the P end and N end of described forward diode model with described dead resistance;
Described forward diode model, reverse breakdown current are zero;
Described Voltage-controlled Current Source, its current value is:
Wherein, cur is the Voltage-controlled Current Source current value, and jrev is the reverse breakdown current coefficient, and Bvrev is the breakdown reverse voltage point, and nrev is the exponential term correction factor of reverse breakdown current, V
AFor Voltage-controlled Current Source with dead resistance tie point voltage, t is environment temperature, k is Boltzmann constant, q is the electric charge constant.
Described forward diode model, the forward working current is:
Wherein, id is the forward working current, and ISeff is the watt current coefficient, and Vd is extraneous bias voltage, and N is the correction factor of current index item, and Vt is physical constant.
Diode simulation circuit model of the present invention, outside forward diode model dio1, add virtual device Voltage-controlled Current Source gdio and dead resistance Rx, Voltage-controlled Current Source gdio and dead resistance Rx are serially connected between the P end and N end of forward diode model dio1, forward diode model dio1 reverse breakdown current is zero, has guaranteed that forward diode model dio1 can not work to the emulation of the reverse breakdown current of diode; Described Voltage-controlled Current Source gdio, when carrying out the diode forward operation simulation, the current value cur of Voltage-controlled Current Source gdio is close to 0, forward working current emulation to diode can not work, and guaranteed that forward diode model dio1 normally plays a role to the forward working current emulation of diode.Diode simulation circuit model of the present invention, because the formula that diode forward working current and reverse breakdown current are simulated separates, exponential term correction factor in two formula also separates, and has changed the limitation of common diode simulation circuit model.Diode simulation circuit model of the present invention can by the match to measured data, obtain final accurate model, the model accuracy and the dirigibility that have improved the diode reverse characteristic.
Description of drawings
The present invention is further detailed explanation below in conjunction with accompanying drawing and embodiment.
The comparison diagram of Fig. 1 diode current voltage curve that to be the i-v curve that obtains of existing diode simulation circuit model emulation obtain with actual measurement;
Fig. 2 is diode simulation circuit model one embodiment schematic diagram of the present invention;
The comparison diagram of Fig. 3 diode current voltage curve that to be the i-v curve that obtains of diode simulation circuit model of the present invention emulation obtain with actual measurement.
Embodiment
Diode simulation circuit model one embodiment of the present invention as shown in Figure 2, comprise the first forward diode model dio1, a Voltage-controlled Current Source gdio, a dead resistance Rx, described Voltage-controlled Current Source gdio is serially connected between the P end and N end of described forward diode model dio1 with described dead resistance Rx;
Described forward diode model dio1, reverse breakdown current are zero, and the forward working current is:
Formula 3;
Wherein, id is the forward working current, and ISeff is the watt current coefficient, and Vd is extraneous bias voltage, and N is the correction factor of current index item, and Vt is physical constant;
Described Voltage-controlled Current Source gdio, its current value is:
Formula 4;
Wherein, cur is the Voltage-controlled Current Source current value, and jrev is the reverse breakdown current coefficient, and Bvrev is the breakdown reverse voltage point, and nrev is the exponential term correction factor of reverse breakdown current, V
AFor Voltage-controlled Current Source gdio with dead resistance Rx tie point A voltage, t is environment temperature, k is Boltzmann constant, q is the electric charge constant.
One preferred embodiment, t is 25 ℃, and Rx is 40 ohm, and Bvrev is 5.45V, and jrev is 1E-14, nrev is 0.55.
Diode simulation circuit model of the present invention, outside forward diode model dio1, add virtual device Voltage-controlled Current Source gdio and dead resistance Rx, Voltage-controlled Current Source gdio and dead resistance Rx are serially connected between the P end and N end of forward diode model dio1, forward diode model dio1 reverse breakdown current is zero, has guaranteed that forward diode model dio1 can not work to the emulation of the reverse breakdown current of diode; Described Voltage-controlled Current Source gdio, when carrying out the diode forward operation simulation, the current value cur of Voltage-controlled Current Source gdio is close to 0, forward working current emulation to diode can not work, and guaranteed that forward diode model dio1 normally plays a role to the forward working current emulation of diode.Diode simulation circuit model of the present invention, because the formula that diode forward working current and reverse breakdown current are simulated separates, exponential term correction factor in two formula also separates, and has changed the limitation of common diode simulation circuit model.Diode simulation circuit model of the present invention can by the match to measured data, obtain final accurate model, the model accuracy and the dirigibility that have improved the diode reverse characteristic.
Described Voltage-controlled Current Source gdio, its current value cur is affected by the exponential term correction factor nrev of reverse breakdown current coefficient jrev, breakdown reverse voltage point Bvrev, reverse breakdown current, the exponential term correction factor nrev of reverse breakdown current coefficient jrev, breakdown reverse voltage point Bvrev, reverse breakdown current and dead resistance Rx are the adjustable parameters that can be used for match, make diode simulation circuit model and diode measured data carry out match by adjusting these parameters, can access the model that a cover can accurately be described diode characteristic.Adopt diode simulation circuit model of the present invention to device simulation with the comparison diagram of device actual measurement as shown in Figure 3, what the figure dotted line represented is the diode current voltage curve that actual measurement obtains, and solid line representative is the i-v curve that diode simulation circuit model of the present invention emulation obtains, and can see that diode simulation circuit model of the present invention can both obtain preferably alignment precision at forward working current and the reverse breakdown current of diode.In addition, diode simulation circuit model of the present invention is owing to having added the dead resistance correction term, and model has also obtained very large improvement in reverse breakdown current saturation region precision.