R_C typically >100R_S, therefore I_C < I_OUT/100 and I_OUT ≈ -(1.25 - (I_CR_C))/R_S

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Other Materials from the Main Document

• Article «A negative current source with PWM input and LM337 output»
• Figure 1. Classic LM337 constant negative current source where I_OUT ≈ V_ADJ/R_S = 1.25/R_S
• Figure 2. R_C typically >100R_S, therefore I_C < I_OUT/100 and I_OUT ≈ -(1.25 - (I_CR_C))/R_S
• Figure 3. An 18 V, 1 A, PWM-programmed grounded load negative current source with a novel LM337 topology. With this topology, accuracy is insensitive to supply rail tolerance. The asterisked resistors are 1% or better and R_S = 1.25 Ω
• Figure 4. Modifications to facilitate wiping out component tolerances including those of U₁ and Z₁ references and all resistors. Note that R_S = 1.1 ohm