Ted was fairly busy his first morning back after vacation. He had a bunch of voice mails and emails to answer. But, Bill and Ted met in the hallway.

Ted says, "Hi, Bill. How did you get on with the op-amp layout last week?"

"Oh, I think I got on really well," Bill says. "I've finished the layout. I'm really pleased with it. I think you'll like it."

"Great. I have a meeting at 11:00, so let's go through it together right after lunch."

After lunch they get together.

Bill says, "Ok, here's my layout. Let me quickly talk you through the floor-plan." Bill begins pointing to all of the devices as he talks about each section.

"I've placed your two PMOS devices, M1 and M2, up at the top of the cell. I've tried to pay attention to all the matching requirements that you were talking about. The devices are both in the same orientation, and I have the gates common in the middle.

"The input differential pair M3 and M4 are placed south of the two PMOS devices on the left-hand side of the layout. I've tried to keep them close to the PMOS devices to try keep the parasitics down. And, also, I've kept the gates fairly close, because I know you were worried about the matching on this."

Bill continues, "Your current source device is on the far right-hand side of the layout. And, I've ringed the whole layout with substrate contacts with the...