Telecom 19-2 Brother Weng
1. The purpose of the experiment
1. Master various settings and methods of AC scanning analysis.
2. Experimental content:
- The common emitter amplifier circuit is shown in the figure below. Try to analyze the magnification of the intermediate frequency area, the upper limit cut-off frequency and the lower limit cut-off frequency, the circuit input resistance and output resistance.
| Component name |
Component library |
illustrate |
| R |
Library/Pspice/Analog.olb |
resistance |
| C |
Library/Pspice/Analog.olb |
capacitance |
| Q2N2222 |
Library/Pspice/Bipolar.olb |
Triode |
| VDC |
Library/Pspice/Sourse.olb |
DC voltage source |
| VAC |
Library/Pspice/Sourse.olb |
AC signal source |
step:
(1) Make a circuit diagram and set the AC of the V2 signal source to 1
(2) Select AC Sweep/Noise in Analysis type, and select General Settings in Options. The analysis frequency of AC Sweep is from 0.01Hz to 1GHz, using decade frequency, and the number of sampling points per decade is 50. Run the simulation.
(3) In the Probe window, enter the amplitude-frequency response expression: DB(V(out)/V(in)), to display the amplitude-frequency characteristic curve of the voltage gain. Activate the ruler, measure and list the IF voltage gain (dB) = (42.280). The lower limit cut-off frequency fL and the upper limit cut-off frequency fH are approximately: fL=(4.0973), fH=(10.000M). (The decibels of the upper limit cut-off frequency fH and the lower limit cut-off frequency are 3 decibels less than the intermediate frequency booster gain (decibels)).
(4) In the Probe window, enter the phase-frequency response expression: P(V(out)/V(in)), to display the phase-frequency characteristic curve of the voltage gain. Start the ruler, measure and list the phase difference in the mid-frequency region (-89.753).
(5) In the Probe window, the characteristic curve of the input resistance is displayed. Input resistance expression: V(in)/I(c2). Start the ruler, measure and list the input resistance in the IF region as approximately (899.637).
2. The circuit is shown in the figure below. Try to analyze the variation range of the lower limit frequency f L when C 5 varies from 1UF to 100UF .
step:
(1) Set up AC analysis. The analysis frequency of AC Sweep is from 0.01Hz to 1GHz, using decade frequency, and the number of sampling points per decade is 50.
(2) Select Parametric sweep.
Sweep variable: Global Parameter;
Parameter name: cval
Sweep type: value list
Set C e to take the table values 1UF, 5UF, 10UF, 20UF, 50UF, 80UF, and 100UF. (Note that the list values are separated by spaces)
(3) After performing the simulation, the amplitude-frequency response curve of the voltage gain is obtained. It can be seen from the figure that when C e changes between 1UF and 100UF, the trend of the lower limit frequency changes.
3. The circuit is as shown in the picture in question 2. Try to analyze the change trend of the output voltage of the circuit when the amplification factor of the triode changes between 20 and 200.
step:
(1) Set up AC analysis. The analysis frequency of AC Sweep is from 0.01Hz to 1GHz, using decade frequency, and the number of sampling points per decade is 50.
(2) Select parameter analysis.
Sweep variable: Model Parameter;
Model type: NPN
Model name: Q2N3904
Parameter name: Bf
Sweep type: Linear
Start value:20 End value:200 Increment value:20
(3) Perform AC scanning analysis to check the output voltage change curve.
4. The circuit is as shown in the picture in question 2. Try to analyze the change of the collector current of the triode in the circuit when the temperature changes between 20 and 100.
step:
(1) Set up AC analysis. The analysis frequency of AC Sweep is from 0.01Hz to 1GHz, using decade frequency, and the number of sampling points per decade is 50.
(2) Select parameter analysis.
Sweep variable:Temperature
Sweep type: Linear
Start value:20 End value:100 Increment value:10
(3) Conduct AC scan analysis. View the change curve of the triode collector current. The expression of transistor collector current is IC(Q2).
5. The negative feedback circuit is shown in the figure below, and R f is the feedback resistance. Perform an AC sweep analysis on the circuit.
beg:
(1) Set the AC scanning analysis, and obtain the output amplitude-frequency response curve and phase-frequency response curve after simulation.
(2) The R f resistance varies between 5K and 30K, and the change curve of the 3dB bandwidth of the gain and R f is analyzed.
Conclusion: It can be seen from the change curve that the change curve of Rf shows that the bandwidth of the passband is widened, and the gain is more stable than before.
(3) If the R f resistor is removed, compare the changes in the output amplitude-frequency response curve, input resistance, and output resistance.
Conclusion: After removing the feedback resistor, the bandwidth becomes narrower, and the input resistance and output resistance remain unchanged. That is, after the introduction of negative feedback, the circuit performance is more stable, the gain-bandwidth product will not change, the gain will decrease, and the bandwidth will widen.
6. The noise calculated in the circuit is usually thermal noise generated on resistors, shot noise and flicker noise generated by semiconductor devices.
step:
(1) Open the \Cadence\SPB_16.6\tools\pspice\Demo_samples\anasim\example file.
(2) Perform AC scan analysis and select noise analysis. Fill in V(OUT2) in Output Voltage, fill in V1 in I/V, and fill in 30 in Interval.
(3), view the output file. The noise and total noise of each component at a frequency of 100Mhz.
(4) In the Probe window, select V (ONOISE) and V (INOISE) in Trace/Add, and check the total output noise voltage of the output node OUT2 and the equivalent input noise voltage calculated at the input node as the frequency changes. Changes.
The introduction of this experiment ends here.
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