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university:courses:electronics:electronics-lab-6 [29 Nov 2018 11:26]
Antoniu Miclaus
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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 ===== 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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 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:​** **Resources:​**
-  * Fritzing files: [[ https://minhaskamal.github.io/DownGit/#/home?​url=https://​github.com/​analogdevicesinc/​education_tools/​tree/​master/​m2k/​fritzing/bjt_current_mirror_bb ​bjt_current_mirror_bb]] +  * 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-6.1543487201.txt.gz · Last modified: 29 Nov 2018 11:26 by Antoniu Miclaus