V_OUT (0 to -10 V and +10 V) versus PWM duty factor, D (0 to 1). The black curve is LM317's V_OUT = 1.25 D/(1 - 0.875 D). The red curve is LM337's V_OUT = -1.25 D/(1 - 0.875 D)

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Other Materials from the Main Document

• Article «Symmetrical 10 V, 1.5 A PWM-programmed power supply»
• Figure 1. LM337, LM317, and CD4053 join forces in a symmetrical 0 to ±10 V PWM programmed power supply.
• Figure 2. V_OUT (0 to -10 V and +10 V) versus PWM duty factor, D (0 to 1). The black curve is LM317's V_OUT = 1.25 D/(1 - 0.875 D). The red curve is LM337's V_OUT = -1.25 D/(1 - 0.875 D)
• Figure 3. The PWM D required for any desired V_OUT. PWM D = |V_OUT|/(0.875 |V_OUT| + 1.25)
• Figure 4. D (x-axis) versus V_OUT (y-axis) is (fairly) close to a logarithmic function, which makes good use of limited 8-bit PWM resolution