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--- university:courses:electronics:electronics-lab-6 [23 Mar 2017 16:06] – [Materials:] Doug Mercer
+++ university:courses:electronics:electronics-lab-6 [25 Jun 2020 22:07] (current) – external edit 127.0.0.1
@@ Line 1: / Line 1: @@
-====== Activity 6. BJT Current Mirror ======
+====== Activity: BJT Current Mirror ======
 ===== Objective: =====
@@ Line 22: / Line 22: @@
 <WRAP centeralign> Figure 1 Current mirror test circuit </WRAP>
+{{ :university:courses:electronics:a6n_f2.png? |}}
+<WRAP centeralign> Figure 2 Breadboard Connection of Current mirror test circuit </WRAP>
 ===== Hardware Setup: =====
-In the current mirror configuration, the opamp 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.
 {{ :university:courses:electronics:a6_f2.png?500 |}}
-<WRAP centeralign> Figure 2 Alt, Simple current mirror test circuit </WRAP>
+<WRAP centeralign> Figure 3 Alt, Simple current mirror test circuit </WRAP>
+{{ :university:courses:electronics:a6n_f4.png? |}}
+<WRAP centeralign> Figure 4 Breadboard Connection of Simple current mirror test circuit </WRAP>
 ===== Procedure: =====
@@ Line 43: / Line 53: @@
 Identical transistors by definition have the same I<sub>S</sub>. In the simple current mirror, both transistors have the same V<sub>BE</sub>. Thus, both transistors will have the same I<sub>C</sub> and if base currents are ignored, Iin = Iout. Actually I<sub>C1</sub>is I<sub>in</sub> - (I<sub>B1</sub> + I<sub>B2</sub>).
+Plot the two waveforms using the Oscilloscope provided by the Scopy tool.
+{{ :university:courses:electronics:a6n_f5.png?500 |}}
+<WRAP centeralign> Figure 5 Current Mirror waveforms, W2 at 10kHz Sample Rate</WRAP>
 ===== Questions: =====
@@ Line 50: / Line 66: @@
 ====== Current Mirror with Base Current Compensation ======
-Modify the simple mirror circuit by adding the base current compensation transistor Q<sub>3</sub> as shown below in figure 3. Repeat the same procedure you followed for the simple mirror circuit.
+Modify the simple mirror circuit by adding the base current compensation transistor Q<sub>3</sub> as shown below in figure 6.
 {{ :university:courses:electronics:a6_f3.png?500 |}}
-<WRAP centeralign> Figure 3 Current Mirror with Base Current Compensation </WRAP>
+<WRAP centeralign> Figure 6 Current Mirror with Base Current Compensation </WRAP>
+=====Hardware Setup=====
+{{ :university:courses:electronics:a6n_f7.png? |}}
+<WRAP centeralign> Figure 7 Breadboard Connection of Current Mirror with Base Current Compensation </WRAP>
+=====Procedure =====
+Repeat the same procedure you followed for the simple mirror circuit.
+{{ :university:courses:electronics:a6n_f8.png?500 |}}
+<WRAP centeralign> Figure 8 Current Mirror waveforms, W2 at 10kHz Sample Rate </WRAP>
 ===== Questions: =====
@@ Line 68: / Line 93: @@
 ====== Wilson Current Mirror ======
-Modify the simple mirror into a Wilson Mirror as shown below in figure 4. Repeat the same procedure you followed for the simple mirror circuit.
+Modify the simple mirror into a Wilson Mirror as shown below in figure 9. Repeat the same procedure you followed for the simple mirror circuit.
 {{ :university:courses:electronics:a6_f4.png?500 |}}
-<WRAP centeralign> Figure 4 Wilson current mirror </WRAP>
+<WRAP centeralign> Figure 9 Wilson current mirror </WRAP>
+=====Hardware Setup=====
+{{ :university:courses:electronics:a6n_f10.png? |}}
+<WRAP centeralign> Figure 10 Breadboard Connection of Wilson current mirror </WRAP>
+=====Procedure =====
+Repeat the same procedure you followed for the simple mirror circuit.
+{{ :university:courses:electronics:a6n_f11.png?500 |}}
+<WRAP centeralign> Figure 11 Current Mirror waveforms, W2 at 10kHz Sample Rate </WRAP>
 ===== Questions: =====
@@ Line 86: / Line 120: @@
 ====== Widlar current mirror ======
-Modify the simple mirror into a Widlar Mirror as shown below in figure 5. Repeat the same procedure you followed for the simple mirror circuit. In addition to the same quantities and graphs, does your data indicate any advantage to this circuit? Any disadvantages?
+Modify the simple mirror into a Widlar Mirror as shown below in figure 12. Repeat the same procedure you followed for the simple mirror circuit. In addition to the same quantities and graphs, does your data indicate any advantage to this circuit? Any disadvantages?
 {{ :university:courses:electronics:a6_f5.png?500 |}}
-<WRAP centeralign> Figure 5 Widlar current mirror </WRAP>
+<WRAP centeralign> Figure 12 Widlar current mirror </WRAP>
+=====Hardware Setup=====
+{{ :university:courses:electronics:a6n_f13.png? |}}
+<WRAP centeralign> Figure 13 Breadboard Connection of Widlar current mirror </WRAP>
+=====Procedure =====
+Repeat the same procedure you followed for the simple mirror circuit.
+{{ :university:courses:electronics:a6n_f14.png?500 |}}
+<WRAP centeralign> Figure 14 Current Mirror waveforms, W2 at 10kHz Sample Rate </WRAP>
 ===== Questions: =====
@@ Line 120: / Line 163: @@
 ===== Directions: =====
-The diode configuration with nearly zero turn on voltage from activity 2 is used here, in figure 6, to make a current mirror. The current input node at the collector of Q<sub>1</sub> (base of PNP Q<sub>3</sub>) is now much closer to ground compared to the conventional current mirror. What advantages would this have over the conventional mirror?
+The diode configuration with nearly zero turn on voltage from activity 2 is used here, in figure 15, to make a current mirror. The current input node at the collector of Q<sub>1</sub> (base of PNP Q<sub>3</sub>) is now much closer to ground compared to the conventional current mirror. What advantages would this have over the conventional mirror?
 {{ :university:courses:electronics:a6_f6.png?500 |}}
-<WRAP centeralign> Figure 6 Low input head room mirror </WRAP>
+<WRAP centeralign> Figure 15 Low input head room mirror </WRAP>
-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?
+=====Hardware Setup=====
+{{ :university:courses:electronics:a6n_f16.png? |}}
-**Return to Lab Activity [[university:courses:electronics:labs|Table of Contents]]**
+<WRAP centeralign> Figure 16 Breadboard Connection of Low input head room mirror </WRAP>
+=====Procedure =====
+Repeat the same procedure you followed for the simple mirror circuit.
+{{ :university:courses:electronics:a6n_f17.png?500 |}}
+<WRAP centeralign> Figure 17 Current Mirror waveforms, W1 at 10kHz Sample Rate </WRAP>
+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]]**

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