Differences
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| university:courses:alm1k:alm-lab-12 [04 Jun 2015 04:00] – [Questions:] Doug Mercer | university:courses:alm1k:alm-lab-12 [04 Sep 2019 16:12] (current) – Changes for new hardware revision Doug Mercer |
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| ======Activity 12: BJT Differential pair====== | ======Activity: BJT Differential pair====== |
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| =====Objective:===== | =====Objective:===== |
| ====Directions:==== | ====Directions:==== |
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| Build the NPN differential pair test circuit shown in figure 2. The connections to the ALM1000 are as indicated in the green boxes. Q<sub>1</sub> and Q<sub>2</sub> should be selected from your available transistors with the best matching of V<sub>BE</sub>. The emitters of Q<sub>1</sub> and Q<sub>2</sub> share a common connection with one end of R<sub>3</sub>. The other end of R<sub>3</sub>is connected to ground (0V) and supplies the tail current. The base of Q<sub>1</sub> is connected to the output of the first arbitrary waveform generator and the base of Q<sub>2</sub> is connected to the output of the second arbitrary waveform generator trough the 20:1 attenuator network. The two collector load resistors R<sub>1</sub> and R<sub>2</sub> connect between the collectors respectively of Q<sub>1</sub> and Q<sub>2</sub> and the positive supply +5V. The two scope inputs CA-In and CB-In are used to measure the differential output as seen across the two 10KΩ load resistors. | Build the NPN differential pair test circuit shown in figure 2. The connections to the ALM1000 are as indicated in the green boxes. Q<sub>1</sub> and Q<sub>2</sub> should be selected from your available transistors with the best matching of V<sub>BE</sub>. The emitters of Q<sub>1</sub> and Q<sub>2</sub> share a common connection with one end of R<sub>3</sub>. The other end of R<sub>3</sub> is connected to ground (0V) and supplies the tail current. The base of Q<sub>1</sub> is connected to the output of the first arbitrary waveform generator, CH A, and the base of Q<sub>2</sub> is connected to the output of the second arbitrary waveform generator, CH B, through the 20:1 attenuator network. The two collector load resistors R<sub>1</sub> and R<sub>3</sub> connect between the collectors respectively of Q<sub>1</sub> and Q<sub>2</sub> and the positive supply +5V. The two Split I/O inputs AIN and BIN are used to measure the differential output as seen across the two 10K load resistors. |
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| {{ :university:courses:alm1k:alm-lab-12_f2.png?600 |}} | {{ :university:courses:alm1k:alm-lab-12_f2.png?600 |}} |
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| ====Hardware Setup:==== | ====Hardware Setup:==== |
| | Both channels A and B should be set to the SVMI Split I/O mode. Both generators should be configured for a 500 Hz sine wave, with Channel A phase set to 90 degrees and Channel B set to 270 degrees ( 180 degrees difference ). The resistor dividers will reduce the signal amplitude seen at the base of Q<sub>1</sub> with respect to the base Q<sub>2</sub> to slightly less than 200 mV. Channel AIN and BIN (Hi-Z Split inputs) should be connected to display the voltage at the collectors of Q<sub>1</sub> and Q<sub>2</sub>. To also display the AWG channel A and B output waveforms we can use the X Math and Y Math traces. From the Curves drop down menu select CA-V, CB-V, X Math and Y Math traces. Open the Math controls screen and enter AWGAwaveform[t] in the X Math Formula entry and AWGBwaveform[t] in the Y Math Formula entry. The Units can be V and the X Axis can be V-A, the Y Axis can be V-B. |
| Both channels A and B should be set to the Split I/O mode with the Term set To 2.5V. Both generators should be configured for a 500 Hz sine wave, with Channel A phase set to 90 degrees and Channel B set to 270 degrees ( 180 degrees difference ). Set both channels with -11 mA Min value and +11 mA Max value. The resistor dividers will reduce the signal amplitude seen at the base of Q<sub>1</sub>with respect to the base Q<sub>2</sub>to slightly less than 200 mV. Channel CA-In and CB-In (Hi-Z inputs) should be connected to display the voltage at the collectors of Q<sub>1</sub> and Q<sub>2</sub>. | |
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| ====Procedure:==== | ====Procedure:==== |
| **For Further Reading:** | **For Further Reading:** |
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| http://en.wikipedia.org/wiki/Differential_amplifier | [[wp>Differential_amplifier|Differential amplifier]] |
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| **Return to ALM Lab Activity [[university:courses:alm1k:alm-labs-list|Table of Contents]]** | **Return to ALM Lab Activity [[university:courses:alm1k:alm-labs-list|Table of Contents]]** |
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