LAB7opamp

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Electrical Engineering

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Feb 20, 2024

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EE 220L, Section #1003 Lab #7: Op Amp I and II 10/18/2023 Javier Correa-Martinez Nicholas Hong

2 Theory (Javier Correa-Martinez): In the most basic circuit, opamps are used as voltage amplifiers. There are several different types of op amps that change the inputs in different ways. They can be found in the majority of electrical appliances. Theory Nicholas Hong: Operational amplifiers are mainly used to amplify an input voltage, and can also be used to invert a signal. The amplifier increases the input voltage, called gain, by connecting resistors to certain parts of the operational amplifier. An inverting amplifier inverts the sign of the input voltage, which means its gain should always be negative. Its gain can be found via the formula; vout/vin=-Rf/Ri Procedure: 1. Voltage Follower First we constructed the voltage-following op-amp circuit shown, then used the function generator to create a 1V pk-pk, 100Hz sine wave, and used it as the input for the circuit. Then, using both channels of the oscilloscope we measured the input and output peak-to-peak voltages. We then found the gain and phase shit between the input and output signals. Next, we found the frequency at which the output becomes distorted and analyzed the shape of the wave. 𝐺𝑎𝑖? = 𝑉??? 𝑉𝑖? = 4 4 = 1

3 Questions What frequency does the output become distorted and what shape does the output waveform take? Around 100khz the output waveform becomes distorted and takes a triangular shape.

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4 What is one practical use for the voltage follower. A voltage follower can be used as a buffer because it draws very little current due to the high input impedance of the amplifier, thus eliminating loading effects while still maintaining the same voltage at the output. 2. Inverting Amplifier First we constructed the inverting op-amp circuit shown, then used the function generator to create a 2V pk-pk, 1kHz sine wave, and used it as the input for the circuit. Then, using both channels of the oscilloscope we measured the input and output peak-to-peak voltages. We then found the gain and phase shit between the input and output signals. Next, we found the frequency at which the output becomes distorted and analyzed the shape of the wave. After we reset the frequency and instead increased the amplitude until clipping started to occur. 𝐺𝑎𝑖? = 𝑉??? 𝑉𝑖? = 28.2 8 = 3.53

5 Questions What frequency does the output become distorted and what shape does the output waveform take? Around 9khz the output waveform becomes distorted and takes a triangular shape.

6 Why does clipping occur and on which alteration of the sine wave does it occur. Clipping occurs around 8V on the output wave which is caused by exceeding the input common- mode voltage range or the input differential voltage range of the op-amp. 3. Inverting Summer First we constructed the inverting summer op-amp circuit shown, then used the function generator to create a 1V pk-pk, 1kHz sine wave, and used it as the input for the circuit. Then, using both channels of the oscilloscope we measured the input and output peak-to-peak voltages. We then found the gain and phase shit between the input and output signals. Next, we found the

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7 frequency at which the output becomes distorted and analyzed the shape of the wave. After we reset the frequency and instead increased the amplitude until clipping started to occur. 𝐺𝑎𝑖? = 𝑉??? 𝑉𝑖? = 28.2 4 = 7.05

8 Questions What frequency does the output become distorted and what shape does the output waveform take? Around 2khz the output waveform becomes distorted and takes a triangular shape. Why does clipping occur and on which alteration of the sine wave does it occur. Clipping occurs around 8V on the output wave which is caused by exceeding the input common- mode voltage range or the input differential voltage range of the op-amp.

9 4. Non-Inverting Amplifier First we constructed the non-inverting op-amp circuit shown, then used the function generator to create a 2V pk-pk, 1kHz sine wave, and used it as the input for the circuit. Then, using both channels of the oscilloscope we measured the input and output peak-to-peak voltages. We then found the gain and phase shit between the input and output signals. Next, we found the frequency at which the output becomes distorted and analyzed the shape of the wave. After we reset the frequency and instead increased the amplitude until clipping started to occur. 𝐺𝑎𝑖? = 𝑉??? 𝑉𝑖? = 28.2 7.99 = 3.53

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10 Questions What frequency does the output become distorted and what shape does the output waveform take? Around 6khz the output waveform becomes distorted and takes a triangular shape. Why does clipping occur and on which alteration of the sine wave does it occur. Clipping occurs around 10V on the output wave which is caused by exceeding the input common-mode voltage range or the input differential voltage range of the op-amp.

11 5. Inverting Integrator First we constructed the inverting op-amp circuit shown, then used the function generator to create a 1V pk-pk, 100Hz square wave, and used it as the input for the circuit. Then, using both channels of the oscilloscope we measured the input and output peak-to-peak voltages. We then found the gain and phase shit between the input and output signals. Next, we found the frequency at which the output becomes distorted and analyzed the shape of the wave. After we reset the frequency and changed the function generator wave to a triangular wave then sine wave. 𝐺𝑎𝑖? = 𝑉??? 𝑉𝑖? = 30.2 4 = 7.55

12 Questions What shape does the distorted output waveform take? The distorted output waveform takes a triangular shape.

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13 What shape does the output waveform take when you change the function generator wave? When the input waveform is change to a triangle so does the output. The same thing happens when you change the input waveform to a sine wave.

14 Why does the circuit integrate the way it does. Since the constantly changing input of the square wave charges and discharges the capacitor, the output signal will be a sawtooth waveform whose output is affected by the RC time constant. Conclusion Javier Correa-Martinez: In this lab we used op amps to create various circuits shown above. The physical equipment was giving us trouble and would not display the proper waveforms on the oscilloscope. Even after switching to a different set up we were still receiving inaccurate results. Therefore, the main source of error was the equipment used. On multisim it seems as if we got the proper waveforms and outputs which allowed for accurate calculations. Conclusion Nicholas Hong: In conclusion of this lab, we used op-amps to create voltage followers and inverting amplifiers. However, we were unable to successfully operate them, giving us inaccurate results. One of the potential sources of error could have been the equipment used. Checking on multiple oscilloscopes, the displayed signal wave was already heavily distorted before any modifications, which was not what was to be expected. The measured gains of the op-amps in parts 1 and 2 were not correct to what they should’ve been. The gain of the voltage follower was significantly

15 larger than 1, and the gain of the inverting amplifier was positive instead of negative. We believe that the equipment, whether it was the measuring equipment or the given op-amps, were faulty.

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