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university:courses:electronics:electronics-lab-8a [05 Mar 2019 12:24] – [Questions:] Antoniu Miclausuniversity:courses:electronics:electronics-lab-8a [20 Jul 2022 20:35] (current) – [Objective:] Doug Mercer
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-====== Activity 8A: A Floating (two terminal) Current Source / Sink ======+====== Activity: A Floating (two terminal) Current Source / Sink ======
  
-===== Objective: =====+=====Objective:=====
  
 The objective of this activity is to investigate the ΔV<sub>BE</sub> concept to produce an output current which is stabilized (less sensitive) to variations of the input voltage level. Feedback is used to build a circuit which produces a constant or regulated output current over a range of supply voltages The objective of this activity is to investigate the ΔV<sub>BE</sub> concept to produce an output current which is stabilized (less sensitive) to variations of the input voltage level. Feedback is used to build a circuit which produces a constant or regulated output current over a range of supply voltages
  
 +=====Background:=====
 +
 +The [[adi>media/en/technical-documentation/data-sheets/AD590.pdf|AD590]] is a 2-terminal integrated circuit temperature transducer that produces an output current proportional to absolute temperature. The schematic diagram of this floating current source is shown in figure 7 of the AD590 datasheet. The a simplified and less accurate version of this concept is used as the experimental circuit in this activity.
 +
 +The AD590 uses a fundamental property of silicon BJT transistors to realize its temperature proportional characteristic. If two identical transistors are operated at a constant ratio of collector current densities, r, then the difference in their base-emitter voltage is (kT/q)(In r). Because both k (Boltzman’s constant) and q (the charge of an electron) are constant, the resulting voltage is directly proportional to absolute temperature (PTAT). For more details please refer to the datasheet.
 ===== Materials: ===== ===== Materials: =====
 ADALM2000 Active Learning Module\\ ADALM2000 Active Learning Module\\
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 <WRAP centeralign> Figure 2 Floating current source (as a sink tied to a negative supply) Breadboard Circuit </WRAP> <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 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.+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: ===== ===== Procedure: =====
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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 |}}
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 <WRAP round download> <WRAP round download>
 **Resources:** **Resources:**
-  * Fritzing files: [[ https://minhaskamal.github.io/DownGit/#/home?url=https://github.com/analogdevicesinc/education_tools/tree/master/m2k/fritzing/float_current_source_bb | float_current_source_bb]] +  * Fritzing files: [[downgit>education_tools/tree/master/m2k/fritzing/float_current_source_bb | float_current_source_bb]] 
-  * LTspice files: [[ https://minhaskamal.github.io/DownGit/#/home?url=https://github.com/analogdevicesinc/education_tools/tree/master/m2k/ltspice/float_current_source_ltspice | float_current_source_ltspice]]+  * LTspice files: [[downgit>education_tools/tree/master/m2k/ltspice/float_current_source_ltspice | float_current_source_ltspice]]
 </WRAP> </WRAP>
  
university/courses/electronics/electronics-lab-8a.1551785078.txt.gz · Last modified: 05 Mar 2019 12:24 by Antoniu Miclaus

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