EEET 2255 Basic Circuit Analysis Electronics Assignment

Project – Frequency Response of the Non-inverting Op-Amp Circuit

Project Aim

Investigate the frequency response of the non-inverting op-amp circuit

Parts List

NI Multisim Live (available online)
NI Analog Discovery II (driving software: Digilent WaveForms)
Components:

o One 741 op-amp o Breadboard and wires o Resistors: 100Ω, 1kΩ, 2 x 10kΩ.

Project Description and Tasks

Part 1: Calculations and Simulations

The op-amp is very popular and has many uses, since it requires few external components and circuitry is easy to design. Figure 1 shows an open-loop op-amp circuit.

Q1: Build the circuit shown in Figure 1 in Multisim Live and use the 3-terminal op-amp model (3T_VIRTUAL). Run an AC simulation sweeping from 1 Hz to 10 GHz (1e10 Hz). Display the output voltage versus frequency using a dB scale for the output voltage. What is the gain of the amplifier (in dB) at 1 Hz and the 3 dB bandwidth of the amplifier (i.e. the frequency where the gain has dropped by 3 dB from its value at 1 Hz)? EEET 2255 Basic Circuit Analysis Electronics Assignment

[4 marks]

Q2: Setup a transient simulation to analyse the amplifier circuit from 0 seconds to 5 seconds. Then open the op-amp settings by double clicking on the op-amp symbol and change the Vomp and Vomn values from the default values to 100 V and -100 V, respectively. This changes the power supply provided to the op-amp. Re-run the transient simulation and explain the differences you see in the output voltage waveform for the two cases.

[4 marks]

Q3: Calculate the overall gain of the circuit shown in Figure 2 under two conditions: (1) the op-amp has infinite open-loop gain (A=∞); and (2) the op-amp has an open-loop gain of A = 200k. Compare your calculated results.

[4 marks]

Q4: Build the circuit shown in Figure 2 in Multisim Live (use the UA741CD op-amp model). Use an AC sweep analysis over the frequency range of 1 Hz to 10 GHz. Compare the simulated gain (at 1 Hz) with the gain calculations from Q3 when: (1) the op-amp has infinite open-loop gain (A=∞); and (2) the op-amp has an open-loop gain of A = 200k. EEET 2255 Basic Circuit Analysis Electronics Assignment

[4 marks]

Q5: From the simulation results obtained in Q4, determine the 3 dB bandwidth of the amplifier. Compare the bandwidth result obtained with the open-loop bandwidth obtained in Q1. How does the feedback connection affect the circuit bandwidth and the circuit gain?

[2 marks]

Q6: For the circuit in Figure 2, run a transient simulation over a time interval of 0 to 5 seconds. Repeat the simulations for Vsource peak voltage values of 0.4 V and 0.1 V. In all three cases, include the gain A = in your output plots. Compare the results with the gain values calculated in Q3 and explain any differences.

[4 marks]

Q7: Comparing the results you obtained in Q1 with those you obtained in Q4, how does the feedback connection affect the circuit bandwidth?

[2 marks]

EEET 2255 Basic Circuit Analysis Electronics Assignment