Hello...

I've been trying to answer to this question and I tried to search in one of the books (Ned Mohan's book) we used in classes but couldn't find the answer, so I need help.

The image in question is below and I need to identify which of the options have the correct waveforms for the given cirucits.
The left plots are the control and input voltages and at the right are the output voltages.

 

Hello,

This is a borderline digital/analog circuit where part of the circuit works in a switching mode and part due to analog qualities.

What you have to do is think about what happens at the output when each transistor is turned on.
Part of the keys to the answer are:
1. Two caps in series with a DC source create 1/2 Vcc when the charge removed each 1/2 cycle is equal to the charge replenished every other 1/2 cycle and dv/dt is not too large, and those are typical assumptions in these kinds of circuits.
2. Two transistors in series with a DC source can not both be turned on at the same time.
3. The output is the differential result of the switching and/or the 1/2 Vcc caused by the two caps.
4. The triangle waves are used to generate the proper pulse widths in time for the PWM, but that is probably not too much of a concern to solve this.

Usually you have to think about each case when you have different things that can turn on and off.

See if that helps you solve this.

 

Oh thanks for replying. I didn't noticed I got a reply.
I'll read this carefully and try to answer the problem later today!

 

1. Two caps in series with a DC source create 1/2 Vcc when the charge removed each 1/2 cycle is equal to the charge replenished every other 1/2 cycle and dv/dt is not too large, and those are typical assumptions in these kinds of circuits.

Ok, so for this I know that output plot for circuit (a) must be 1/2 of the input voltage! That means (a) -> i. And if this is correct, the only option is the first one! But I would like to keep analysing the other waveforms for the other circuit.

2. Two transistors in series with a DC source can not both be turned on at the same time.

Are you referring to the circuit on the left or the one on the right or both?

3. The output is the differential result of the switching and/or the 1/2 Vcc caused by the two caps.

I'm not sure what should I take from this one!