DC and Bias Point Simulations > BJT Noise Fig., S-Params, Gain, Stability, and Circles vs. Bias

Description

This simulates the S-parameters and noise parameters of a device, versus bias voltage and current, at a single frequency. You specify the collector voltage sweep range and the base current sweep range, and the single frequency for S-parameter and noise analysis. The optimal source and load impedances for minimum noise figure and for maximum gain are computed, as well as the available gain circles, power gain circles, noise circles, and source and load stability circles.

Needed to Use Schematic

Nonlinear BJT model

Main Schematic Settings

Sweep ranges for base current and collector voltage and frequency for S-parameter analysis.

Data Display Outputs

BJT_SP_NF_Match_Circ.dds, "NF, SP, Gains at all Bias Pts." page:

• Minimum noise figure versus VCE and base current
• dB(S21), dB(S12), dB(S11), and dB(S22) versus collector voltage and base current
• Maximum available gain versus base current and collector voltage
• Associated power gain (with input matched for minimum noise figure and output conjugately matched) versus collector voltage and base current

BJT_SP_NF_Match_Circ.dds, "Matching at 1 Bias Point" page:

• Minimum noise figure and dB(S21) versus collector current at a collector voltage selected by moving a marker on the I-V curves.
• DC I-V curves
• Smith chart with traces of the optimal source reflection coefficients for minimum noise figure, and the following reflection coefficients (gammas) at the selected bias point:
  • Gamma source for minimum noise figure
  • Gamma load for maximum power gain when input is terminated for minimum noise figure
  • Gamma source for simultaneous conjugate match (without regard to noise)
  • Gamma load for simultaneous conjugate match (without regard to noise)
• Listing columns of data corresponding to the bias point selected by moving a marker on the I-V curves:
  • VCE
  • IC
  • Approximate DC power consumption
  • S-parameters, dB
  • Maximum available power gain, dB
  • Minimum noise figure, dB
  • Sopt for minimum noise figure in polar coordinates and in magnitude and phase
  • Zopt for minimum noise figure
  • Associated power gain in dB, if the input is matched for minimum noise figure and then the output is matched for maximum power gain
  • Corresponding load impedance for associated power gain
  • Source and load impedances for simultaneous conjugate matching (without regard to noise)
  • Input and output impedances when source and load are terminated in 50 ohms
  • Stability factor, K
  • Frequency of the S-parameter simulations

BJT_SP_NF_Match_Circ.dds, "Circles_Ga_Gp_NF_Stability" page:
All at one bias point selected by moving a marker on the device's I-V curves:

• • Stability factor, K, and source stability circles. Note that the Smith Chart size is fixed, so if the stability circles are far outside the Smith Chart, they will not be displayed. If you change the Smith Chart scaling to Auto Scale, the circles will be visible.
  • Available gain and noise circles on one Smith Chart, and power gain circles on a different Smith Chart.
  • Minimum noise figure, source impedance (Zopt) required to achieve this noise figure, and the optimal load impedance for power transfer when the source impedance is Zopt
  • Maximum available gain, and the source and load impedances required for simultaneous conjugate matching (only valid if K>1)
  • Noise figure with the simultaneous conjugate match condition
  • Noise figure, transducer power gain, and optimal load impedance if the source impedance is chosen arbitrarily by moving a marker (GammaS) on a Smith Chart. This is useful if you must make some compromise between noise and gain, or if you need to avoid an unstable region.
  • Transducer power gain, and optimal source impedance and corresponding noise figure, if the load impedance is chosen arbitrarily by moving a marker (GammaL) on a Smith Chart. This is useful if you need to avoid an unstable region.

Schematic Name

BJT_SP_NF_Match_Circ

Data Display Name

BJT_SP_NF_Match_Circ.dds