Why the second transistor is free
Chapter 10 spent six benches on a circuit that only works because two devices are the same. Not the same value — the same. The tanh split, the cancelling common mode, the offset that came out at 257 µV rather than tens of millivolts: every one of those depended on two transistors agreeing with each other to a fraction of a percent.
Now look at your parts drawer. Two resistors from the same bag agree to 1% if you paid for 1%, and 5% if you did not. Nobody sells you a bag of transistors that match. And yet the chapter said matching on a die is something you get almost for nothing, if you are willing to spend area on it. Both of those things are true, and the gap between them is enormous. This lesson measures it.
The misconception
“A chip costs what it costs because of the silicon.” It is the natural thing to think. Silicon is the exotic material, the wafer is the thing in the photographs, the fab is the expensive building. So the price must be the price of area. Once you believe that, matching looks like a straightforward purchase: better matching needs more area, more area costs more silicon, more silicon costs more money.
The arithmetic in this lesson kills the idea in one move. Matching on a die really does cost area, and the area really does grow fast. It is still about two thousand times cheaper than buying the same matching as discrete parts — and you can pay ten times more per wafer without denting that. Whatever you are paying for when you buy precision, it is not the silicon.
Commit before you touch anything
You need two components matched to 0.1%. Option one: two 0.1% discrete resistors from a distributor. Option two: two transistors laid out side by side on a 28 nm-class wafer, sized big enough to hit the same 0.1%. How much cheaper is the silicon?
One manufacturing event, not two
Here is the actual reason, and it has nothing to do with silicon being cheap. Two discrete resistors are two separate manufacturing events. Different substrates, possibly different lots, possibly different years, trimmed by different machines, sitting at different temperatures on your board. The difference between them is the difference between two independent draws from a wide distribution, and the only way to narrow it is to measure parts and throw away the ones that miss.
Two transistors on one die are one manufacturing event. Same wafer, same lot, same implant, same oxide growth, same anneal, same lithography exposure, microns apart, at the same temperature for the rest of their lives. Everything that would have made them differ has already been applied to both of them equally. What is left is only the local random part — individual dopant atoms landing where they land, the ragged edge of a printed line — and that part obeys a law.
The consequence is a hard exchange rate. Because σ falls as the square root of area, halving your mismatch costs four times the area. There is no cleverness that gets around it; a common-centroid layout removes gradients, not randomness. Going from 0.1% to 0.01% is a hundredfold area increase — the 24 µm square becomes a 240 µm square, which is a visible speck on a die photograph and the reason precision analogue blocks look so absurdly large next to logic.
The exponent is not what integration changed
Put the two curves on the bench and something worth noticing appears. Silicon costs a hundred times more per decade of matching, because of that square-root law. The discrete parts do not follow the same rule at all. Going from 1% to 0.1% costs about 12× at the distributor, which is close to linear — that first decade is bought by sorting parts, and sorting scales with how many you throw away. Going from 0.1% to 0.01% costs about 142×, because at that point you have changed technology, changed vendor, and started paying for a measurement rather than a component.
So integration did not repeal the exponent. Over the range on the bench the silicon curve is the steeper of the two. What integration moved is the intercept, by three or four orders of magnitude. Making matching better is expensive everywhere. Having matching at all is what became free.
And this is where analogue stops scaling
Now do the experiment the industry actually ran. Take the same 0.1% pair from a 45 nm-class process at $3,000 a wafer to a 22 nm-class process at $20,000 a wafer. The matching coefficient improves by about 2.7×, so the area you need falls by about seven. The wafer costs 6.7× more. The two effects very nearly cancel, and the pair comes out at 0.94× its old cost. Fifteen years of scaling; no change.
Over those same years digital logic got several times denser per generation and a logic gate got cheaper every time. Analogue did not, because analogue does not buy transistors — it buys area, matching, headroom and noise, and none of those four scaled. That is the whole argument in one number, and lesson 3 is about what a company does when it finds itself holding that number.
In the wild
The instrumentation amplifier that is mostly a resistor network. An in-amp’s common-mode rejection is set by how well three resistor pairs track. Nobody builds one from loose parts. Vishay sells thin-film networks with ratio tolerance to 0.02% and tracking temperature coefficient of ±5 ppm/°C against ±25 ppm/°C absolute — the ratio is five times better than the values, for exactly the reason above: they are on one substrate, made in one event.
Laser trimming. If you cannot get matching from geometry, you buy it back afterwards by burning a notch in a thin-film resistor while watching a meter. It works, it is why a 0.01% part exists at all, and it is a per-part operation performed by a machine on a component — which is precisely the cost that integration deleted.
Why your op-amp datasheet has an offset drift spec. Chapter 10 showed VOS is proportional to VT and therefore to absolute temperature. Trimming at 25 °C cannot remove a slope. The part that gets you microvolts across temperature is a chopper, which measures its own offset thousands of times a second — buying matching with digital effort instead of area, because area got expensive and digital did not.
Before you move on
A colleague says on-die matching is cheap because silicon is cheap. What is the strongest single piece of evidence against that?
Nobody who designs chips owns a factory
Until the mid-1980s, a company that designed chips built them. Design and manufacturing were one business because a process and a design were developed against each other and could not be separated. Then in 1987 Morris Chang founded a company in Hsinchu that would manufacture other people’s designs and compete with none of them, and that single structural decision split the industry into two halves that have been diverging ever since.
The scale of the split now is easy to state and hard to absorb. In 2025 TSMC took $122.5 billion of revenue, which TrendForce puts at 69.9% of the entire global foundry market, up from 64.4% the year before. It ran 305 distinct process technologies and made 12,682 different products for 534 customers. It owns no product of its own.
The reason the split happened, and the reason it will not un-happen, is the number at the bottom of a foundry’s cash-flow statement. TSMC spent $40.9 billion on capital equipment in 2025 against that $122.9 billion of revenue. In July 2026 it raised its guidance for the current year from $52–56 billion to $60–64 billion, which its CFO put at roughly 36% of sales. Nvidia, whose revenue in the quarter to July 2026 was $96.2 billion, spent $2.68 billion on property and equipment in the same period. That is 2.8%.
Part of that money buys machines from a company with no competitor. A current low-numerical-aperture EUV scanner runs around $200 million; the High-NA generation, ASML’s EXE:5200, is reported at about $400 million and there are fewer than a dozen in existence. When the Belgian research institute imec took delivery of one in March 2026, Reuters put the price at $400 million. There is one supplier on earth. That fact will matter again in lesson 3.
Commit before you touch anything
A 4 mm² microcontroller on a 28 nm process, sold ten million times. Of what it costs you to bring each one into existence, roughly what fraction is the silicon?
The only equation in this interlude
What a chip costs you, per chip, is two terms that behave in opposite ways:
- Silicon per good die. The wafer price divided by how many working dies come off it. Flat in volume — the millionth wafer costs what the first one did.
- NRE per die. Everything you paid before the first chip existed, divided by how many you sell. Falls as 1/volume, forever.
Working dies, not dies. A wafer is a fixed disc of about 70,700 mm² and you pay for all of it. Big dies fit worse and, much more importantly, catch more defects: at a defect density of about 0.11 per square centimetre, a 100 mm² die yields near 90% and an 800 mm² die yields 44%. Doubling die area does not double silicon cost — from 100 mm² upward, each doubling multiplies it by between 2.3 and 3.3.
Nobody knows what a wafer costs
Here the sourcing runs into a wall, and the wall is the lesson. No foundry has ever published a wafer price. Every figure you have read is a supply-chain rumour reported by trade press, and they do not agree. For a 3 nm wafer the published estimates run from $18,000 to $27,000 — a spread of 50% on the single most-quoted number in chip economics.
| Node | Low published | High published | Spread |
|---|---|---|---|
| 28 nm | $3,000 | $4,000 | 1.3× |
| 7 nm | $9,500 | $9,500 | one figure only |
| 5 nm | $15,000 | $18,500 | 1.2× |
| 3 nm | $18,000 | $27,000 | 1.5× |
| 2 nm | $22,000 | $30,000 | 1.4× |
Design cost is worse. The most-cited figures come from International Business Strategies: $249 million at 7 nm, $449 million at 5 nm, $581 million at 3 nm, $725 million at 2 nm. But IBS’s own numbers move: its 2014 chart put 16/14 nm near $310 million and its 2018 chart put the same node at $106 million. Brian Bailey, writing in Semiconductor Engineering in 2023, applied that same discount forward and got roughly $280 million at 5 nm and $160 million at 7 nm; SemiAnalysis has said the IBS figures run 50 to 66% above what companies actually spend. The bench draws both readings as separate lines. They sit 1.4 to 1.6× apart on total cost per chip — which looks like a narrow gap only because the vertical axis spans six decades — and neither of them is wrong.
In the wild
Multi-project wafer shuttles. If a full mask set is the barrier, share one. Universities and startups buy a slot on a shuttle run — a few thousand dollars at 65 nm, tens of thousands at 28 nm — and get a few dozen dies back. It exists for exactly the reason this bench shows: at low volume the mask set, not the silicon, is what stops you.
Why the microcontroller in your project box is on an ancient node. Drag the bench to 28 nm and 4 mm², then to 3 nm and the same area. The silicon barely matters either way; the NRE goes up by an order of magnitude. There is no volume at which a $2 part earns back a $600 million design. Mature nodes are not a failure to keep up. They are the correct answer.
Chiplets. If yield collapses with die area, stop making big dies. Interlude I noted that Nvidia’s B200 reaches 208 billion transistors across two pieces of silicon rather than one. Set the bench to 800 mm², read the yield, then halve the area and read it again. That difference is the entire commercial case for advanced packaging, and it is why ASE exists.
Before you move on
You are choosing between 28 nm and 3 nm for a part you expect to sell 200,000 times. Which consideration dominates?
Where the money actually lands
Seven companies stand between a physics paper and a chip on your board. One sells the lithography machines. One owns the factories. One packages and tests what comes out. One does all three for its own products. One designs and owns nothing. Two design analogue parts and kept their own factories anyway. They all report their numbers every quarter, so you can simply look.
The obvious way to look is gross margin: of every dollar of revenue, how much is left after the direct cost of producing the thing. On that measure the ranking is not subtle. Nvidia, which owns no fab, reported 75.0% for the quarter ending July 2026. TSMC, which owns the fabs, reported 67.7%. ASE, which packages and tests, reported 21.0% across the group. Design captures more per dollar than manufacturing, and manufacturing captures more than assembly.
That is the story everyone tells, and it is incomplete in a way that this lesson’s bench makes visible in one click.
Commit before you touch anything
Gross margin ignores what a company spends rebuilding its factory. Subtract each firm’s capital spending, as a share of its own revenue, from its gross margin. TSMC starts second of the seven on gross margin. Where does it finish?
Margin is not the same as keeping the money
A foundry’s gross margin is calculated after the cost of running the fab, but the fab has to be rebuilt continuously to stay at the leading edge, and that spending sits somewhere else on the accounts. TSMC’s capital budget for 2026 is $60–64 billion, about 36% of sales. Intel’s is over $20 billion on a business running near $64 billion a year. ASE announced roughly $10.5 billion. Nvidia spent $2.68 billion in a quarter on $96.2 billion of revenue.
Subtract that and the spread across the seven widens from 54 points to 91 points. The ordering inverts around one axis: whoever has to rebuild the factory pays for the privilege of being essential. TSMC is not less profitable than Nvidia because it is worse at business. It is less profitable per dollar of revenue because the thing it sells requires it to buy $400 million machines from a company that has no competitor, forever, and Nvidia does not.
Which brings us back to the differential pair
Look at where Analog Devices and Texas Instruments sit. Both design analogue parts. Both own their own fabs, which by the logic of the fabless split they should have sold twenty years ago. Both sit near the top on both measures — ADI second, TI level with ASML for third — ahead of the leading-edge foundry.
Lesson 1 is why. Matching costs the same on a modern node as it did fifteen years ago, so there is nothing at the leading edge for an analogue part to go and get. Lesson 2 is the other half: analogue product lines sell in thousands of distinct part numbers at modest volume each, which is the worst possible place to be standing when NRE is the dominant term. So the analogue companies stayed on mature nodes, where the wafer is cheap and the mask set is cheap, and they kept their factories — because a mature fab is paid off, and a paid-off fab does not need $60 billion a year.
They are also buying something a foundry menu does not offer. Analogue processes carry thick gate oxides for parts that must survive 40 volts, precision poly resistors, metal-insulator-metal capacitors, trimmable elements, laser fuses. A leading-edge logic process has none of that, because logic does not need it. Owning the fab is how you own the option to add a process step for one product family.
| Company | Gross margin | Capex / revenue | Difference |
|---|---|---|---|
| Nvidia — fabless | 75.0% | 2.8% | 72.2% |
| Analog Devices — analogue IDM | 67.3% | 3.5% | 63.8% |
| ASML — lithography | 54.0% | 4.3% | 49.7% |
| Texas Instruments — analogue IDM | 61.0% | 11.4% | 49.6% |
| TSMC — foundry | 67.7% | 36.0% | 31.7% |
| Intel — IDM | 40.4% | 31.3% | 9.1% |
| ASE — package and test | 21.0% | 40.0% | −19.0% |
One warning about reading that table. It is a single quarter of a boom, in an industry with a violent cycle. TSMC’s gross margin was 59.5% in the third quarter of 2025 and 67.7% in the second of 2026; Intel’s was 27.5% a year ago and 40.4% now. The ordering is structural and has held for years. The numbers are a photograph of one moment.
In the wild
The 741 is still for sale. A part designed in 1968, on a process nobody would call a node, still shipping because the tooling is long paid for and the design has earned back its NRE approximately a million times over. Every term in lesson 2’s equation has gone to zero except the silicon, and the silicon was never the expensive part.
TI building 300 mm fabs for analogue. Sherman, Texas and Lehi, Utah — large-scale 300 mm plants for parts that do not need a leading-edge node at all. The gain is not smaller transistors, it is more area per wafer for the same processing cost, which is precisely the currency lesson 1 says analogue trades in. TI has said it is nearing the end of a six-year elevated spending cycle and expects to spend $2–3 billion in 2026, down from about $4.6 billion in 2025.
The queue for packaging. An AI accelerator now needs three things at once: a wafer slot, an advanced packaging slot and a memory allocation. Any one without the other two ships nothing. That is why the least profitable link in the chain by gross margin is simultaneously the one raising capital spending fastest — scarcity is not the same thing as margin, and this quarter it is sitting in the packaging house.
Before you move on
Why do Analog Devices and Texas Instruments still own fabs when Nvidia, Apple and AMD do not?