Designing Stage

In the LAB we built our circuit design as shown in our previous update on a SK10 board, the circuit worked perfectly. However we discovered it was not going below 4V when we vary the transistor R12, so we had to go back to the circuit to know where the problem came from. The circuit was then adjusted to obtain a voltage  below 4V and even up to 0.1V. Below is the edited circuit diagram and  the output waveform.

Figure 6: The new Design

  

Figure 7: Output from the new design.

The output of the new design when compared to that of the older design is better. The two extra voltages provide bipolar voltages to drive the operational amplifier. The negative voltage is used to generate a reference voltage below ground so that the output can be adjusted down to zero.