Question 13.1: FINDING THE PERFORMANCE OF AN OP-AMP INVERTING AMPLIFIER An ...
FINDING THE PERFORMANCE OF AN OP-AMP INVERTING AMPLIFIER
An inverting amplifier is shown in Figure 13.4. Use PSpice to plot the DC transfer characteristic if the input is varied from −1 to +1 V with an 0.2-V increment. (a)Use the op-amp of Figure 13.1(a) as a subcircuit; its parameters are A_{o} = 2 × 10^{5}, R_{i} = 2 MΩ, and R_{o} = 75 Ω. (b) Use the op-amp of Figure 13.2 as a subcircuit; its parameters are R_{i} = 2 MΩ, R_{o} = 75 Ω, C_{1} = 1.5619 μF, and R_{1} = 10 kΩ. (c) Use the macromodel of Figure 13.3 for the UA741.
The listing of the subcircuit OPAMP-DC for Figure 13.1(a) is as follows:
| * Subcircuit definition for OPAMP-DC: .SUBCKT OPAMP-DC 1 2 3 4 * model name Vi− Vi+ Vo+ Vo− RIN 1 2 2MEG RO 5 3 75 EA 5 4 2 1 2E+5 ; Voltage-controlled voltage source * End of subcircuit definition: .ENDS OPAMP-DC ; End of subcircuit definition |
The listing of the subcircuit OPAMP-AC for Figure 13.2 is as follows:
| * Subcircuit definition for OPAMP-AC: .SUBCKT OPAMP-AC 1 2 3 4 * model name Vi− Vi+ Vo+ Vo− RI 1 2 2MEG GB 4 5 1 2 0.1M ;Voltage-controlled current source R1 5 4 10K C1 5 4 1.5619UF EA 4 6 5 4 2E + 5 ;Voltage-controlled voltage source RO 6 3 75 .ENDS OPAMP-AC ;End of subcircuit definition |
(a) The PSpice schematic for a DC op-amp model is shown in Figure 13.5(a), and the DC op-amp model is shown in Figure 13.5(b).
The listing of the circuit file with the DC op-amp model is as follows:
| SOURCE VIN 1 0 DC 1V CIRCUIT R1 1 2 10K RF 2 3 100K ANALYSIS .DC VIN −1V 1V 0.1V ; DC sweep .PROBE ; Graphics post-processor .END |
The plot of the transfer characteristic using the DC op-amp model of Figure 13.1(a) is shown in Figure 13.6. The expected gain is R_{F} /R _{1} = 100/10 = 10.
(b) The PSpice schematic for an AC op-amp model is shown in Figure 13.7(a), and the AC op-amp model is shown in Figure 13.7(b).
The listing of the circuit file with the AC op-amp model is as follows:
| SOURCE VIN 1 0 DC 1V CIRCUIT R1 1 2 10K RF 2 3 100K ANALYSIS .DC VIN −1V 1V 0.1V ;DC sweep .PROBE ;Graphics post-processor .END |
The plot of the transfer characteristic using the AC op-amp model of Figure 13.2 is shown in Figure 13.8. No difference is expected from that obtained with a DC
signal. However, the output will be dependent on the frequency of the input signal.
(c) The PSpice schematic is shown in Figure 13.9 with a built-in op-amp schematic model.
The listing of the circuit file with the UA741 macromodel is as follows:
| SOURCE VIN 1 0 DC 1V CIRCUIT R1 1 2 10K RF 2 3 100K ANALYSIS .DC VIN −1V 1V 0.1V ; DC sweep .PROBE ; Graphics post-processor .END |
The plot of the transfer characteristic using the UA741 macromodel of Figure 13.3 is shown in Figure 13.10. A macromodel affects the characteristics because it has saturation limits. The voltage gain is 4.98.
