Questions -
1. Design an op-amp circuit that meets the following specifications. Your design can be done with one or two op amps. Your instructor may give you a different design.
Important: Show all work. Draw a completely labeled schematic of your design that shows the exact values of all components.
a. The op-amp circuit must have an adjustable, non-inverting overall voltage gain from +2 to +10. The circuit has a 47 kΩ load resistor connected from the last op amp's output terminal to ground.
b. The circuit input resistance must be a ≥ 50 kΩ.
c. Your design is limited to a maximum of two op-amps and seven resistors, one of which is a variable 50 kΩ resistor (potentiometer). The potentiometer resistance is 0 Ω when adjusted to one extreme of its range and 50 kΩ at the other extreme.
d. When the potentiometer is adjusted to one extreme position the overall circuit voltage gain should be +2. When the variable resistor is adjusted to its other extreme position the overall circuit voltage gain should be +10.
Now in LTSpice or similar circuit simulator:
2. For the circuit you designed in the prelab:
a. Perform time domain simulations of two configurations of the circuit. For the first configuration replace the potentiometer by its 0 Ω minimum resistance. For the second situation replace the potentiometer by its 50 kΩ maximum resistance.
b. Use a detailed 741 op amp model that has power supply pin connections. It may be called LM741 or uA741 or similar. You must use independent dc voltage sources set to +15 V and -15 V as power supplies for the op amp model.
Replace your fixed resistors with the closest commercially-available 5% tolerance resistor value. The resistor value does not have to be one in your pans kit. Keep the potentiometer's maximum resistance at 50 kΩ.
Note: if you use LTspice, there are no 741 op amps in the library. Choose an LT1001 op amp instead.
c. Use a 500 mVp-p, 1 kHz sine wave input. Display the input and output waveforms on the same plot for each configuration.
- Use cursors to measure the peak output voltage and note it on the schematic.
- Calculate the voltage gain from each simulation.
- Save copies of the schematics and plots.