##### From Wideband Amplifier Design

## 2.8 AN EXAMPLE

For an example, I will use a real-world transistor NEC part number NE851M03. It is an RF NPN small-signal device with an *f _{t}* approximately equal to 8 GHz at

*I*= 20 mA, and

_{C}*V*= 3 V. For purposes of this book, it has the advantage of being fairly well characterized with SPICE parameters, packaging parameters and "s-parameters" provided by the manufacturer. The actual parameters are given in Appendix A. With these data, one can now begin to compare the accuracy of the high-frequency models against the actual SPICE model.

_{CE}Assume that we are using the NE851M03 in the emitter-follower circuit shown in Figure 2-22 with a 4 pF load. The operating point is *V _{CE}* = 3 V,

*I*= 20 mA, making

_{C}*g*= 0.7737 S. There is a 10 nH inductor in the base. The NE851M03 has

_{m}*f*= 7.95 GHz at this operating point.

_{t}This gives *T _{t}* = = 20.03 ps and

*C*=

_{?}*g*= 15.5 pF.

_{m}T_{t}From the SPICE parameters table, we see that the transistor has an emitter resistance *R _{eb}* = 1.7 ?. (The actual SPICE parameter is labeled

*R*.) This gives

_{E}Because *C _{eb}* is in series with

*C*, the combination is

_{?}*C*

_{bt}: *R _{bb}*, as listed in the SPICE table, is 1 ?

*. R*

##### Products & Services

##### Topics of Interest

2.9 ADDING RESISTANCE TO THE BASE From the stability chart shown in Figure 2-26, we observed that the circuit would be stable only for those source impedances that were represented by the "stable...

3.6 SPICE-Modeling Parameters This section briefly describes some of the important model parameters for diodes, bipolar transistors, and MOS transistors, used during a SPICE simulation (Massobrio and...

The f t of a transistor is given by the following equation, (A.1) where C jc is the collector base junction capacitance, C je is the emitter base junction capacitance, R c is the collector bulk...

3.8 SPICE Simulations The circuit diagrams, netlist files, and output data associated with SPICE simulations of selected examples are presented in this section. The device models, unless explicitly...

3.10 Problems For the problems in this chapter and all future chapters, assume the following transistor parameters: npn bipolar transistors: ? = 100 V A = 80 V ? b = 13 ps ? s = 4 ns r b = 330 ? n...