How do I get a Bode plot with the J2111A?
It is not possible to get a Bode plot using this method, only the phase margin; however it is an accurate method for assessing the performance where other methods are not possible.
The J2111A along with the Bode-100 can provide the phase margin of a control loop without access to the control loop. This is convenient in that it allows a stability assessment without lifting any wires or breaking any connections. It also works with fixed voltage regulators where there is no access to the control loop, as well as assessing the stability of a negative resistance switching regulator with an input filter. The result is a singular solution, providing only the phase margin. The method is quite accurate, but requires real and imaginary roots for the solution, so the results can only be determined for values below 70 Degrees. Above this the result is displayed as >70 Degrees.