And then there was noise: The mystery of the missing ENOB, Part 2

Editor’s note: This is the second post in a three-part ENOB blog series. You can find part 1 here: And then there was noise: The mystery of the missing ENOB if you missed it.

Drip … drip … drip …

Drip … drip … drip …

A broken bottle leaks liquid off a table onto the floor. The sound shatters the quiet of the room, each drip louder than the last.

Drip … drip … drip …

Drip … drip … drip …

PGA sits on the ground, stunned, his mind racing.

What happened to ENOB?

In front of him, 16 bits lay strewn across the floor; 10 are missing.

Where did they go?

PGA looks up.

An angry mob surrounds him.

The burly man gets up.

“HOW SHOULD I KNOW?” he yells. “What about Modulator – it’s his job to shape the noise. Maybe he messed this all up!”

Modulator raises an eyebrow.

“Me? I’m a fourth-order modulator, buddy. My noise-shaping curve would blow your mind. Besides, it’s hard to make a mistake outputting data at 2.5 SPS – we can’t run any slower than that.”

PGA surveys the room for someone else to accuse.

“W-what about Digital Filter, then? Maybe she got jealous of ENOB always taking credit for her work. So she decides to make him look bad, gets a little liberal with her cut-off frequency, and – ”

“Let me stop you right there, PGA,” Digital Filter interrupts. “You don’t have to worry about me or my coefficients. Any high-frequency noise Modulator outputs, I remove – no more, no less. Not even for a punk like ENOB.”

Dead ends everywhere. With attenuating resolve, PGA looks around desperately. He stops at Multiplexer


PGA opens his mouth –

Their words saturate the air as the two men lock eyes.

Nobody moves.

Nobody breathes.

“Maybe he’s right –”

A voice rings out from the back of the room. All eyes shift to a shadowy figure sitting at a table in the corner raising a drink to its lips. PGA and Multiplexer break their death stare to peer into the darkness. As they do, the shadow stands up and walks into the light.

“– maybe you need me.”

“And just who the heck are you?” asks Multiplexer.

PGA shakes his head and sighs: “Op Amp.”

“That’s no way to treat your brother ,” smirks Op Amp. He turns to Multiplexer. “I’m just like PGA here, only my gain isn’t capped at 32V/V. I’m the solution to your problem.”

Multiplexer cracks his knuckles. “It’s been a long night, Op Amp. You’d better start making sense or I’m going to find out what your nonlinear region of operation looks like.”

Op Amp takes another sip of his drink. “It’s simple: You don’t have enough gain – that’s why you need me,” he explains calmly. “Let me amplify the signal first , then pass it along to you. My added gain will easily increase the number of bits you can resolve.”

PGA nods his head. “Yeah, exactly – more gain. It was right there the whole time.”

“Let’s sample this signal again,” Op Amp says. “Only this time, I’ll go first, then Multiplexer, then you – we’ll have those bits back in no time.”

The brothers go to work, and after several cycles, Digital Filter hands the bag of bits to Multiplexer, as Op Amp confidently turns to the crowd.

“How many bits are there now?”

Behind him, Multiplexer pulls the bits out one at a time.


The smile fades from Op Amp’s face as he whirls around. He grabs the bits from Multiplexer, counts them feverishly, then hurls the bag across the room.

“No no NO NO NO! This has to work! More gain always works!”

The mob gathers once more as the panicked man looks up. Op Amp turns to his brother. “Check the noise tables in the data sheet – this doesn’t make any sense!”

PGA flips through the pages on his phone until he reaches the right spot. “Got it!”

Op Amp grabs the phone, stares at it in disbelief, then glances up in horror.

The doors of the building fly off the hinges as a crack of lightning streaks through the night sky. The burst of light erupts behind a monstrous shadow standing in the doorway.

Everyone looks over to see the figure standing there, his coat whipping in the wind, rain beating down around him.

Obscured by the night, they cannot make out his legs … his arms … his chest … or his face. In fact, the only thing they can see is the unmistakable fury of …

The eyes have returned! But for what? Money? Revenge? Maybe he didn’t pay his tab?

To finish unraveling the mystery of the missing ENOB, check back for the thrilling conclusion to “And then there was noise.”

Until then …

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