$$CTR = \fracI_CI_F \times 100%$$
| Rank | CTR Min (%) | CTR Max (%) | Conditions | |------|-------------|-------------|-------------| | A | 50 | 150 | I_F = 5 mA, V_CE = 5V, Ta=25°C | | B | 80 | 240 | I_F = 5 mA, V_CE = 5V, Ta=25°C | | C | 130 | 400 | I_F = 5 mA, V_CE = 5V, Ta=25°C | | D | 200 | 600 | I_F = 5 mA, V_CE = 5V, Ta=25°C | a1458 optocoupler datasheet
If the output only drops to 1.5V, the A1458 has a damaged phototransistor or a false datasheet. $$CTR = \fracI_CI_F \times 100%$$ | Rank |
| Parameter | Typical Expected Value | Why It Matters | | :--- | :--- | :--- | | | 3,750 Vrms – 5,000 Vrms | Safety compliance (UL, VDE). For A1458, check if it meets reinforced insulation. | | Current Transfer Ratio (CTR) | 50% – 600% (depending on bin) | The gain of the coupler. Low CTR (<50%) indicates an old or slow device. | | Rise/Fall Time (tr/tf) | 2 – 18 µs | Determines max switching speed (typically < 100 kHz for standard types). | | Input Forward Current (IF) | 50 mA (max) / 10 mA (typical) | Prevents burning out the internal LED. | | | Current Transfer Ratio (CTR) | 50%