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university:courses:electronics:electronics-lab-6 [24 Aug 2018 04:48]
Trecia Agoylo Added scopy screenshots to the activities
university:courses:electronics:electronics-lab-6 [25 Jun 2020 22:07] (current)
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-====== Activity ​6. BJT Current Mirror ======+====== ActivityBJT Current Mirror ======
  
 ===== Objective: ===== ===== Objective: =====
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 <WRAP centeralign>​ Figure 1 Current mirror test circuit </​WRAP>​ <WRAP centeralign>​ Figure 1 Current mirror test circuit </​WRAP>​
  
-{{ :​university:​courses:​electronics:​a6n_f2.png?​500 |}}+{{ :​university:​courses:​electronics:​a6n_f2.png?​ |}}
  
 <WRAP centeralign>​ Figure 2 Breadboard Connection of Current mirror test circuit </​WRAP>​ <WRAP centeralign>​ Figure 2 Breadboard Connection of Current mirror test circuit </​WRAP>​
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 ===== Hardware Setup: ===== ===== Hardware Setup: =====
  
-In the current mirror configuration,​ the op amp serves as a virtual ground at the mirror input (base) node to convert the voltage steps from AWG 2 ( W2 output ) into current steps through the 1KΩ resistor. The collector voltage is swept using a ramp from AWG 1(output W1) set to 3V peak to peak with the offset to 1.5V. V<​sub>​CE</​sub>​ of output device Q<​sub>​2</​sub>​ is measured differentially by scope inputs 1+, 1-. The mirror output current is measured by scope inputs 2+. 2- across 1KΩ resistor, R<​sub>​2</​sub>​.+In the current mirror configuration,​ the op amp serves as a virtual ground at the mirror input (base) node to convert the voltage steps from AWG 2 ( W2 output ) into current steps through the 1KΩ resistor. The collector voltage is swept using a ramp from AWG 1(output W1). Load the stairstep.csv file, set amplitude ​to 3V peak-to-peak with the offset to 1.5V.  
 +V<​sub>​CE</​sub>​ of output device Q<​sub>​2</​sub>​ is measured differentially by scope inputs 1+, 1-. The mirror output current is measured by scope inputs 2+. 2- across 1KΩ resistor, R<​sub>​2</​sub>​.
 If you don't want to use the op-amp configuration the following simplified configuration can be used as well. If you don't want to use the op-amp configuration the following simplified configuration can be used as well.
  
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 <WRAP centeralign>​ Figure 3 Alt, Simple current mirror test circuit </​WRAP>​ <WRAP centeralign>​ Figure 3 Alt, Simple current mirror test circuit </​WRAP>​
  
-{{ :​university:​courses:​electronics:​a6n_f4.png?​500 |}}+{{ :​university:​courses:​electronics:​a6n_f4.png?​ |}}
  
 <WRAP centeralign>​ Figure 4 Breadboard Connection of Simple current mirror test circuit </​WRAP>​ <WRAP centeralign>​ Figure 4 Breadboard Connection of Simple current mirror test circuit </​WRAP>​
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 =====Hardware Setup===== =====Hardware Setup=====
-{{ :​university:​courses:​electronics:​a6n_f7.png?​500 |}}+{{ :​university:​courses:​electronics:​a6n_f7.png?​ |}}
  
 <WRAP centeralign>​ Figure 7 Breadboard Connection of Current Mirror with Base Current Compensation </​WRAP>​ <WRAP centeralign>​ Figure 7 Breadboard Connection of Current Mirror with Base Current Compensation </​WRAP>​
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 <WRAP centeralign>​ Figure 9 Wilson current mirror </​WRAP>​ <WRAP centeralign>​ Figure 9 Wilson current mirror </​WRAP>​
 =====Hardware Setup===== =====Hardware Setup=====
-{{ :​university:​courses:​electronics:​a6n_f10.png?​500 |}}+{{ :​university:​courses:​electronics:​a6n_f10.png?​ |}}
  
 <WRAP centeralign>​ Figure 10 Breadboard Connection of Wilson current mirror </​WRAP>​ <WRAP centeralign>​ Figure 10 Breadboard Connection of Wilson current mirror </​WRAP>​
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 <WRAP centeralign>​ Figure 12 Widlar current mirror </​WRAP>​ <WRAP centeralign>​ Figure 12 Widlar current mirror </​WRAP>​
 =====Hardware Setup===== =====Hardware Setup=====
-{{ :​university:​courses:​electronics:​a6n_f13.png?​500 |}}+{{ :​university:​courses:​electronics:​a6n_f13.png?​ |}}
  
 <WRAP centeralign>​ Figure 13 Breadboard Connection of Widlar current mirror </​WRAP>​ <WRAP centeralign>​ Figure 13 Breadboard Connection of Widlar current mirror </​WRAP>​
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 =====Hardware Setup===== =====Hardware Setup=====
-{{ :​university:​courses:​electronics:​a6n_f16.png?​500 |}}+{{ :​university:​courses:​electronics:​a6n_f16.png?​ |}}
  
 <WRAP centeralign>​ Figure 16 Breadboard Connection of Low input head room mirror </​WRAP>​ <WRAP centeralign>​ Figure 16 Breadboard Connection of Low input head room mirror </​WRAP>​
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 Ideally the collector of PNP Q<​sub>​3</​sub>​ would be connected to some negative voltage with respect to ground. Try connecting the collector of Q<​sub>​3</​sub>​ to the negative board supply Vn. What happens? Can the input node of the mirror get even closer to ground now? Ideally the collector of PNP Q<​sub>​3</​sub>​ would be connected to some negative voltage with respect to ground. Try connecting the collector of Q<​sub>​3</​sub>​ to the negative board supply Vn. What happens? Can the input node of the mirror get even closer to ground now?
 +
 +<WRAP round download>​
 +**Resources:​**
 +  * Fritzing files: [[downgit>​education_tools/​tree/​master/​m2k/​fritzing/​bjt_current_mirror_bb | bjt_current_mirror_bb]]
 +  * LTspice files: [[downgit>​education_tools/​tree/​master/​m2k/​ltspice/​bjt_current_mirror_ltspice | bjt_current_mirror_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-6.1535078923.txt.gz · Last modified: 24 Aug 2018 04:48 by Trecia Agoylo