PSU EET 331 - Composite Amplifiers (5 pages)

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Composite Amplifiers



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Composite Amplifiers

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Pages:
5
School:
Penn State University
Course:
Eet 331 - Electronic Design
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ELECTRICAL ENGINEERING TECHNOLOGY PROGRAM EET 331 ELECTRONIC DESIGN LABORATORY EXPERIENCES LABORATORY EXPERIENCE Composite Amplifiers The goal of this laboratory experience is double First students are introduced to Operational Amplifiers other than the 741 used in previous experiences In particular you will work with 2 Operational Amplifiers with very different DC and AC specifications powered with 5 VDC The second goal is to investigate the characteristics of the Composite Amplifiers taking advantage of the benefits of specific devices while trying to minimize the effects of their shortcomings This experiment has been adapted from the course EET 368 Electrical and Computer Engineering Technology Department Purdue University SECTION 1 DC characteristics of the AD817 Operational Amplifier We will investigate the DC characteristics of this Operational Amplifier by using an Inverting Amplifier 1 1 Design the schematic for an Inverting Amplifier using the AD817 with a gain of 82 and an input impedance of 10 k 1 2 Read the specifications of the AD817 Evaluate the typical and worst case values of offset voltage at the output of the Inverting Amplifier that we can expect Explain to your instructor how did you arrive to this number Voffset typical Voffset worst case 1 3 Build the Inverting Amplifier that you designed in 1 1 Do not forget to include the decoupling capacitors Connect them directly to the power pins Remember that this Operational Amplifier will be powered with 5 VDC For input signal use a sine wave 20 mVp no DC offset at 100 Hz 1 4 Monitor the output of the Inverting Amplifier with the oscilloscope If the signal is distorted reduce the amplitude of the input signal If the output appears to be oscillating connect small decoupling capacitors in parallel with the 47 F EET 331 Composite Amplifier Lab 1 5 1 5 Measure and record the gain of the Inverting Amplifier as well as the DC offset voltage Use the DMM to record the DC offset voltage more accurately 1 6 Compare your results with the typical and worst case DC offset predictions from 1 2 Are your results consistent If not find out where you may have problems SECTION 2 DC characteristics of theLTC1049 Operational Amplifier We will investigate the DC characteristics of the LTC1049 Operational Amplifiers by using the same method as before 2 1 Design the schematic for an Inverting Amplifier using the LTC1049 with a gain of 82 and an input impedance of 10 k 2 2 Read the specifications of the LTC1049 Evaluate the typical and worst case values of offset voltage at the output of the Inverting Amplifier that we can expect Explain to your instructor how did you arrive to this number Voffset typical Voffset worst case 2 3 Build the Inverting Amplifier that you designed in 2 1 Do not forget to include the decoupling capacitors Connect them directly to the power pins Remember that this Operational Amplifier will be powered with 5 VDC For input signal use a sine wave 20 mVp no DC offset at 100 Hz 2 4 Monitor the output of the Inverting Amplifier with the oscilloscope If the signal is distorted reduce the amplitude of the input signal If the output appears to be oscillating connect small decoupling capacitors in parallel with the 47 F 2 5 Measure and record the gain of the Inverting Amplifier as well as the DC offset voltage Use the DMM to record the DC offset voltage more accurately 2 6 Compare your results with the typical and worst case DC offset predictions from 2 2 Are your results consistent If not find out where you may have problems EET 331 Composite Amplifier Lab 2 5 SECTION 3 AC characteristics of the LTC1049 Operational Amplifier We will investigate the AC characteristics of the LTC1049 Operational Amplifier using the same Inverting Amplifier used in Section 2 In particular we will evaluate the 3 dB cutoff frequency of the Inverting Amplifier 3 1 Apply the same input signal use a sine wave 20 mVp no DC offset at 100 Hz Measure and record the output voltage ensuring that the output signal is not distorted 3 2 Increase the frequency of the input signal until the value of the output voltage drops 3 dB This means that the voltage you measured is equal to 0 707 times the voltage measured in 3 1 The frequency at which this happens is the 3 dB cutoff frequency 3 3 Using the specifications of the LTC1049 Operational Amplifier evaluate the expected cutoff frequency for your circuit Expected 3dB cutoff frequency specifications Measured 3b cutoff frequency from 3 2 3 4 Are your results consistent If not re evaluate your measurements or your technique SECTION 4 AC characteristics of the AD817 Operational Amplifier As you can expect we will use the same method to evaluate the AC characteristics of the AD817 Operational Amplifier as we did before 4 1 Build the 82 gain Inverting Amplifier that was built in Section 1 4 2 Apply the same input signal use a sine wave 20 mVp no DC offset at 100 Hz Measure and record the output voltage ensuring that the output signal is not distorted 4 3 Increase the frequency of the input signal until the value of the output voltage drops 3 dB This means that the voltage you measured is equal to 0 707 times the voltage measured in 3 1 The frequency at which this happens is the 3 dB cutoff frequency 4 4 Using the specifications of the AD 817 Operational Amplifier evaluate the expected cutoff frequency for your circuit Expected 3dB cutoff frequency specifications Measured 3b cutoff frequency from 4 3 4 5 Are your results consistent If not re evaluate your measurements or your technique EET 331 Composite Amplifier Lab 3 5 SECTION 5 DC versus AC characteristics of Operational Amplifiers 5 1 Based on all your observations and measurements what can you say about the AC and DC characteristics of these two Operational Amplifiers Is there an Operational Amplifier that performs the best at both DC and AC SECTION 6 The Composite Amplifier The composite amplifier tries to combine the optimal characteristics of two very different Operational Amplifiers The resulting amplifier should have the best DC and AC characteristics of the 2 Op Amps used to build it 6 1 Build the circuit shown below Use the value of R1 and Rf that were used in Section 1 1 Rf 5V 47uF R1 1 AD817 Vout 470nF 5V 47uF 47uF 5V R2 LTC1049 1M R3 10k R4 220 EET 331 Composite Amplifier Lab 47uF 5V 4 5 6 2 Connect at the input of the Composite Amplifier sine wave 20 mVp no DC offset at 100 Hz 6 3 Measure the output signal with an oscilloscope If the output is


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