Nested sweep

Notice that two values are displayed in the Simulation Status window. The bottom line changes quickly and is the main sweep variable, Vs. The line second to the bottom is the nested sweep variable, BV. Notice that for each value of BV, Vs is swept from -15 to +15. Logically, the primary sweep loop executes inside the secondary sweep loop. That is, BV is set to 1 and Vs is swept from -15 to +15. Then BV is set to 2, and Vs is swept from —15 to +15. Then BV is set to 3, and Vs is swept from -15 to +15, and so on. When the analysis is finished, Probe will run. Add the trace V(VL) (press the INSERT key) ... 

For each value of VGS, we want to sweep VDS from 0 to 15 volts. Thus, we want VGS to be our nested sweep variable and VDS to be our main sweep variable. Note also that for jFETs we must sweep VGS from zero to a negative value. Fill in the DC Sweep and Secondary Sweep dialog boxes as shown ... 

We will now generate Hfe versus Ic curves at different temperatures. This is a typical curve found in most data sheets for BJTs. We will use almost the same Secondary Sweep that we used in Section 4.F.2, except that for the Secondary Sweep we will vary temperature rather than VCe- We will use the same circuit and setup as in Section 4.F.2, but we will modify the Nested Sweep. We will start with the circuit from the previous example ... 

The nested DC Sweep can be used to generate characteristic curves for transistors. We will illustrate generating these curves using a BJT. Wire the circuit below ... 

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