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| university:courses:electronics:electronics-lab-6 [29 Nov 2018 11:26] – Antoniu Miclaus | university:courses:electronics:electronics-lab-6 [23 Aug 2019 12:50] – Antoniu Miclaus |
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| ====== Activity 6. BJT Current Mirror ====== | ====== Activity: BJT Current Mirror ====== |
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| ===== Objective: ===== | ===== Objective: ===== |
| ===== 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: [[ 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]] |
| | * LTspice files: [[ https://minhaskamal.github.io/DownGit/#/home?url=https://github.com/analogdevicesinc/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]]** |
