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Fig. 1.4. Test Circuit.  Basic setup we tried.

Fig. 1.4. Class AB amplifier.

Fig. 1.5.  We added additional opamp to see if the total gain would increase which it did.

Fig. 1.5.

4-c.  Our current model is a two-stage class AB amplifier with opamp and Darlington pairs.   We settled on using a unity-gain op. amp to protect the input device.  We also used another two opamp to act as the stage 1 voltage gain stage.  We used a variable resistance box to vary the voltage gain across opamp 2.  We used diodes to split the signal to upper and lower half.  This gave us the Class AB setup so that our transistors can work more efficiently.  We used four diodes to ensure quality filtering and security to our circuit in case one of the diodes blew (which causes a reaction of a short circuit), we can prevent the stage 2 circuit from being damaged.  Gives us extra time in other words.  We can smell something isn’t right (the burning smell).  Then we can analyze and locate the problem(s).  We used TIP 30 and TIP 31 BJT’s right now since we had an bag full of these items provided by Electronic 2 students who were finished with their laboratory section.  In our final model, we do foresee using MOSFET’s which will cut the 90 degree phase shift that we observed between the input and output current both in simulation

ECE 45125/1/2002

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