Member level 5
Hi, I am designing a bandgap reference as shown below and I am measuring the loop gain of the circuit of (Vob-Voa)/(Via-Vib). By changing the size of the cascode transistor that is circled, I could get two different frequency response of the loop gain. The graph on the left is obtained when the cascode transistor is small. Is the graph obtained on the right showing a stable loop? I am not able to explain the change in phase plot in different cases. All the transistors are in saturation in both cases. Please explain to me. Thanks.