Question 1

How is Notional's fCash AMM different from an auction-cleared fixed-rate market like Term Finance?

Accepted Answer

Term Finance and similar protocols collect bids and offers over a window, then clear every matched participant at one uniform price once per auction round — the rate only exists after the auction settles. Notional's fCash markets are a continuous automated market maker: a liquidity pool holds both fCash and cash (the underlying asset), and the implied fixed rate is readable at any instant from the pool's own balance, the same way a spot AMM price is readable from its reserves. There is no clearing event and no waiting for a round; every trade immediately moves the pool and immediately moves the rate.

Question 2

What do rateScalar and rateAnchor actually control in the fCash curve?

Accepted Answer

The exchange rate between fCash and cash is a logit curve: exchangeRate = (1/rateScalar) × ln(proportion / (1 − proportion)) + rateAnchor. rateAnchor sets where the curve is centered — it's the exchange rate (and therefore the implied rate) when the pool is perfectly balanced at a 50/50 proportion of fCash to cash. rateScalar sets the steepness: a larger rateScalar flattens the curve so a given trade moves the rate less (lower slippage), while a smaller rateScalar makes the same trade swing the rate much further. Both are governance-set per market and typically widen as a maturity nears expiry so the curve doesn't get too steep right before settlement.

Question 3

What does "proportion" mean and why does it drive the rate?

Accepted Answer

Proportion is simply how much of the pool's combined value is fCash versus cash: proportion = fCashBalance / (fCashBalance + cashBalance). A proportion near 1 means the pool is almost all fCash and very little cash — that happens when borrowers have pulled a lot of cash out by pushing fCash in, so the market prices a high fixed rate to attract lenders back in. A proportion near 0 means the pool is mostly cash and thin on fCash, which happens when lenders have piled in, so the market prices a low rate because cash is abundant relative to fixed-rate demand.

Question 4

Why does a lend or borrow trade move the rate, and is that the same thing as slippage on a token swap?

Accepted Answer

Yes, mechanically it's the same phenomenon as slippage on a constant-product token AMM, just applied to fCash instead of a token pair. Borrowing removes cash from the pool and adds fCash to it, pushing proportion up and the implied rate up along the curve; lending does the reverse. The bigger the trade relative to the pool's total depth, the further proportion moves and the more the rate slips between the price you see before the trade and the rate you actually realize after it — exactly like a large token swap moving further down a bonding curve than a small one.

Question 5

What does this calculator not capture about the real Notional market?

Accepted Answer

This model uses the published logit exchange-rate formula and a simplified single-step execution price (trade size divided by the pre-trade marginal rate) to size the resulting cash amount, rather than integrating the exact curve trade-by-trade the way the live contract does — so real realized slippage on-chain will differ slightly from the number shown here. It also doesn't model trading fees, the periodic widening of rateScalar as a market approaches maturity, oracle rate smoothing the protocol uses for collateral valuation, or liquidity provider fee income. Treat the output as a model of the curve's shape and direction, not an execution quote.

想定元本 fCash AMM 暗示固定金利計算ツール

fキャッシュプール

曲線に合わせて取引のサイズを決定する

清算価格ではなくカーブ

DeFi が固定金利を発見する 4 つの方法と、曲線の形状が重要な理由