From Wideband Amplifier Design


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 C = 20 mA, and V CE = 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.

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 C = 20 mA, making g m = 0.7737 S. There is a 10 nH inductor in the base. The NE851M03 has f t = 7.95 GHz at this operating point.

This gives T t = = 20.03 ps and C ? = g mT t = 15.5 pF.

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 E.) This gives

Because C eb is in series with C ?, the combination is C bt:

R bb, as listed in the SPICE table, is 1 ? . R

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Phototransistors are solid-state light detectors with internal gain that are used to provide analog or digital signals. They detect visible, ultraviolet and near-infrared light from a variety of sources and are more sensitive than photodiodes. This category includes photodarlingtons. 
Transistors are electronic devices made of semiconductor material that amplify a signal or open or close a circuit.
Flip-flops are digital logic devices that synchronize changes in output state (1 or 0) according to a clocked input.
Small-Signal Bipolar Transistors (BJT)
Small-signal bipolar transistors (BJT) are semiconductors that amplify small AC or DC signals. They consist of a base n-type or p-type layer sandwiched between emitter and collector layers of the opposite type.
Resistors are electrical components that oppose the flow of either direct or alternating current. They are used to protect, operate, or control circuits.

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...

3.10 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...

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...