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university:courses:electronics:electronics-lab-13a [01 Apr 2017 17:02] – [Directions:] Doug Mercer | university:courses:electronics:electronics-lab-13a [25 Oct 2017 05:20] – Trecia Agoylo | ||
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===== Hardware Setup: ===== | ===== Hardware Setup: ===== | ||
- | The waveform generator, W1, should be configured for a 1 KHz sine wave with 3.0 volt amplitude peak amplitude and 0 offset. | + | Channel one of the scope should be connected to display the output of the first generator and both scope channels 1 and 2 should be set to display 1V per division. |
+ | {{ : | ||
- | ===== Procedure: ===== | + | <WRAP centeralign> |
- | Next, apply power and adjust the waveform generator so that W1 is a 100 Hz triangle wave with 0V offset and 3.0 V amplitude values. Use the oscilloscope in the x-y mode to observe the voltage-transfer curve of the circuit. Record the curve on paper, label all breakpoints, | ||
- | Switch the scope to just the time display mode, and adjust the waveform generator | + | ===== Procedure: ===== |
+ | The waveform generator, W1, should be configured for a 1 KHz sine wave with 6.0 volt amplitude | ||
+ | {{ : | ||
- | • Starting with the amplitude = 0 V, gradually increase it until you just begin to see an signal on scope channel 2 appear at the output. For what range of amplitude values of W1 can we say that both BJT's are essentially off? Confirm this by observing the voltages of the current-sensing resistances R<sub>1</ | + | <WRAP centeralign> Figure 3 Push - Pull Output stage Waveforms |
- | • Raise W1 to 3.0V amplitude | + | Next, apply power and adjust the waveform generator so that W1 is a 100 Hz triangle wave with 0V offset and 3.0 V amplitude |
- | • Repeat, but with W1 raised a 5.0V amplitude value; and comment. | + | {{ : |
- | Simulate the circuit of figure 1 using QUCS, compare with your lab findings, and justify any differences. | + | <WRAP centeralign> |
===== Questions: ===== | ===== Questions: ===== | ||
+ | Record the curve on paper, label all breakpoints, | ||
+ | |||
+ | Switch the scope to just the time display mode, and adjust the waveform generator so that W1 is a 1 kHz sine wave with the amplitude = 0 V. | ||
- | Add questions here: | + | • Starting with the amplitude = 0 V, gradually increase it until you just begin to see a signal on scope channel 2 appear at the output. For what range of amplitude values of W1 can we say that both BJT's are essentially off? Confirm this by observing the voltages of the current-sensing resistances R< |
+ | |||
+ | • Raise W1 to 6.0V amplitude value, and record the amplitude of the output waveform as well as the collector currents of the BJTs, which can be found via Ohm's law from the voltages across R< | ||
+ | |||
+ | • Repeat, but with W1 raised a 10.0V amplitude value; and comment. | ||
+ | |||
+ | Simulate the circuit of figure 1 using QUCS, compare with your lab findings, and justify any differences. | ||
====== Reducing Output Distortion: ====== | ====== Reducing Output Distortion: ====== | ||
The large amount of distortion at the zero-crossings in the basic push-pull stage of figure 1 is a result of a dead zone when both the NPN and PNP emitter followers are off. The waveform' | The large amount of distortion at the zero-crossings in the basic push-pull stage of figure 1 is a result of a dead zone when both the NPN and PNP emitter followers are off. The waveform' | ||
- | |||
===== Directions: ===== | ===== Directions: ===== | ||
- | With the power turned off, assemble the circuit of figure | + | With the power turned off, assemble the circuit of figure |
{{ : | {{ : | ||
- | <WRAP centeralign> | + | <WRAP centeralign> |
- | If we examine, in figure | + | If we examine, in figure |
+ | ===== Hardware Setup: ===== | ||
+ | |||
+ | Channel one of the scope should be connected to display the output of the first generator and both scope channels 1 and 2 should be set to display 1V per division. The breadboard connections are shown in figure 2. | ||
+ | {{ : | ||
+ | |||
+ | <WRAP centeralign> | ||
+ | |||
+ | ===== Procedure: ===== | ||
+ | The waveform generator, W1, should be configured for a 1 KHz sine wave with 6.0 volt amplitude peak amplitude and 0 offset. Using scope channel 1 to observe the input at W1 and scope channel 2 to observe the output of the amplifier at R< | ||
+ | {{ : | ||
+ | |||
+ | <WRAP centeralign> | ||
===== Questions: ===== | ===== Questions: ===== | ||
- | • Display the input / output transfer curve of the circuit of figure | + | • Display the input / output transfer curve of the circuit of figure |
• Apply a 1-kHz sine wave of 0 V offset and various amplitudes, and verify that the circuit yields Vout ? Vin all the way down to small amplitudes. What is the upper limit on the amplitude of W1 before the circuit starts to distort? Justify quantitatively in terms of the transfer curve just observed. | • Apply a 1-kHz sine wave of 0 V offset and various amplitudes, and verify that the circuit yields Vout ? Vin all the way down to small amplitudes. What is the upper limit on the amplitude of W1 before the circuit starts to distort? Justify quantitatively in terms of the transfer curve just observed. | ||
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Measure the input impedance by inserting a 10K? resistor in series with the signal generator (between W1 and the emitters of Q< | Measure the input impedance by inserting a 10K? resistor in series with the signal generator (between W1 and the emitters of Q< | ||
- | Simulate the circuit of figure | + | Simulate the circuit of figure |
====== Another Configuration: | ====== Another Configuration: | ||
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{{ : | {{ : | ||
- | <WRAP centeralign> | + | <WRAP centeralign> |
+ | ===== Hardware Setup: ===== | ||
+ | |||
+ | Channel one of the scope should be connected to display the output of the first generator and both scope channels 1 and 2 should be set to display 1V per division. The breadboard connections are shown in figure 2. | ||
+ | {{ : | ||
+ | |||
+ | <WRAP centeralign> | ||
+ | |||
+ | ===== Procedure: ===== | ||
+ | The waveform generator, W1, should be configured for a 1 KHz sine wave with 6.0 volt amplitude peak amplitude and 0 offset. Using scope channel 1 to observe the input at W1 and scope channel 2 to observe the output of the amplifier at R< | ||
+ | {{ : | ||
+ | |||
+ | <WRAP centeralign> | ||
===== Questions: ===== | ===== Questions: ===== | ||
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**Return to Lab Activity [[university: | **Return to Lab Activity [[university: | ||
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