4.7 Noise in Bipolar Transistors

Chapter 4.7 Noise in Bipolar Transistors

Radio Frequency Integrated Circuit Design Second Edition Book
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Radio Frequency Integrated Circuit Design Second Edition Book

  • 4.7 Noise in Bipolar Transistors 83resulted in a somewhat reduced value of 60 GHz. At 71.8 GHz, the impedance of Cp is calculated to be -j3.167W. Thus, the approximation that this impedance is much less than rb or rp is justified. Calculation of fmax results in a value of 104.7 GHz. The real part of the output impedance is calculated as 98.6W. We note that the reactive part of the output impedance will be cancelled out by the matching network.4.7  Noise in Bipolar TransistorsIn addition to the thermal noise in resistors, as discussed in Chapter 2, transistors also have other types of noise. These will be discussed next.4.7.1  Thermal Noise in Transistor ComponentsThe components in a transistor that have thermal noise are rb, rE, and rc. Given a resistor value R, a noise voltage source must be added to the transistor model of value 4kTR, as discussed in Chapter 2.Figure 4.8  Normalized fT, gm, and Cp versus bias current. Normalization is with respect to the values at the optimal fT point.Table 4.1  Example Transistors Transistor SizeParameter1´4´15´ IoptfT (mA) 0.552.47.9Cp (fF)50200700Cm (fF)2.726.9623.2rb (W)6520.85.0