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university:courses:electronics:electronics-lab-8a [14 Dec 2012 21:29] – [Questions:] Doug Merceruniversity:courses:electronics:electronics-lab-8a [25 Jun 2020 22:07] – external edit
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-====== Activity 8A: A Floating (two terminal) Current Source / Sink ======+====== Activity: A Floating (two terminal) Current Source / Sink ======
  
 ===== Objective: ===== ===== Objective: =====
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 ===== Materials: ===== ===== Materials: =====
-Analog Discovery Lab hardware\\+ADALM2000 Active Learning Module\\
 Solder-less breadboard\\ Solder-less breadboard\\
 1 - 500Ω Variable Resistor, Potentiometer\\ 1 - 500Ω Variable Resistor, Potentiometer\\
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 ===== Directions: ===== ===== Directions: =====
  
-Build the circuit shown in figure 1 on your solder-less breadboard. The green boxes indicate where to connect the Discovery instruments. PNP transistors Q<sub>1</sub>, Q<sub>2</sub> and Q<sub>3</sub> form a current mirror with a gain of two, the output current is twice the input current. NPN transistors Q<sub>4</sub>, Q<sub>5</sub> and Q<sub>6</sub> along with variable resistor R<sub>1</sub> form the ΔV<sub>BE</sub> part of the circuit. Resistor R<sub>2</sub> is used to measure the current flowing in the circuit ( scope channel 2 ) as the voltage across the circuit changes ( scope channel 1 ).+Build the circuit shown in figure 1 on your solder-less breadboard. The green boxes indicate where to connect the ADALM2000. PNP transistors Q<sub>1</sub>, Q<sub>2</sub> and Q<sub>3</sub> form a current mirror with a gain of two, the output current is twice the input current. NPN transistors Q<sub>4</sub>, Q<sub>5</sub> and Q<sub>6</sub> along with variable resistor R<sub>1</sub> form the ΔV<sub>BE</sub> part of the circuit. Resistor R<sub>2</sub> is used to measure the current flowing in the circuit ( scope channel 2 ) as the voltage across the circuit changes ( scope channel 1 ).
  
 {{ :university:courses:electronics:a18a_f1.png?600 |}} {{ :university:courses:electronics:a18a_f1.png?600 |}}
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 ===== Hardware setup: ===== ===== Hardware setup: =====
  
-Configure waveform generator AWG1 as a triangle wave with a frequency of 100 Hz and an amplitude of 5 V with 0 V offset. The scope display should be set in both voltage vs. time and in XY mode with channel 1 on the horizontal axis and channel 2 on the vertical axis. Be sure to turn on the power supply only after you have completed and double checked your connections.+{{:university:courses:electronics:float_curr_src_vn-bb.png|}} 
 + 
 +<WRAP centeralign> Figure 2 Floating current source (as a sink tied to a negative supply) Breadboard Circuit </WRAP> 
 + 
 +Configure waveform generator AWG1 as a triangle wave with a frequency of 100 Hz and an amplitude of 10 V peak-to-peak with 0 V offset. The scope display should be set in both voltage vs. time and in XY mode with channel 1 on the horizontal axis and channel 2 on the vertical axis. Be sure to turn on the power supply only after you have completed and double checked your connections. 
 + 
 +===== Procedure: ===== 
 + 
 +<WRAP centeralign>{{:university:courses:electronics:float_curr_src_vn-wav.png?500|}}</WRAP> 
 + 
 +<WRAP centeralign> Figure 3 Floating current source (as a sink tied to a negative supply) XY plot </WRAP>
  
 ===== Questions: ===== ===== Questions: =====
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 ===== Prove the floating nature of circuit: ===== ===== Prove the floating nature of circuit: =====
  
-In figure 1 we referenced the negative end of the circuit to a negative power supply. To prove that this circuit is truly a floating current source, rearrange your breadboard to look like figure 2 and repeat your measurements.+In figure 1 we referenced the negative end of the circuit to a negative power supply. To prove that this circuit is truly a floating current source, rearrange your breadboard to look like figure 5 and repeat your measurements.
  
 {{ :university:courses:electronics:a18a_f3.png?600 |}} {{ :university:courses:electronics:a18a_f3.png?600 |}}
  
-<WRAP centeralign> Figure 2 Floating current source (as a source tied to a positive supply) </WRAP>+<WRAP centeralign> Figure 4 Floating current source (as a source tied to a positive supply) </WRAP> 
 + 
 +===== Hardware setup: ===== 
 + 
 +{{:university:courses:electronics:float_curr_src_vp-bb.png|}} 
 + 
 +<WRAP centeralign> Figure 5 Floating current source (as a sink tied to a positibe supply) Breadboard Circuit </WRAP> 
 + 
 +===== Procedure: ===== 
 + 
 +<WRAP centeralign>{{:university:courses:electronics:float_curr_src_vp-wav.png?500|}}</WRAP> 
 + 
 +<WRAP centeralign> Figure 6 Floating current source (as a sink tied to a positive supply) XY plot </WRAP>
  
 ===== Questions: ===== ===== Questions: =====
  
 Is there any measurable difference in the current vs. voltage characteristics for the circuit used as a current sink vs. a current source? Is there any measurable difference in the current vs. voltage characteristics for the circuit used as a current sink vs. a current source?
 +
 +<WRAP round download>
 +**Resources:**
 +  * Fritzing files: [[downgit>education_tools/tree/master/m2k/fritzing/float_current_source_bb | float_current_source_bb]]
 +  * LTspice files: [[downgit>education_tools/tree/master/m2k/ltspice/float_current_source_ltspice | float_current_source_ltspice]]
 +</WRAP>
  
 **Return to Lab Activity [[university:courses:electronics:labs|Table of Contents]]** **Return to Lab Activity [[university:courses:electronics:labs|Table of Contents]]**
university/courses/electronics/electronics-lab-8a.txt · Last modified: 20 Jul 2022 20:35 by Doug Mercer

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