Hello,
For LVPECL output, 240-ohm emitter resistor to GND is recommended. What is the recommended range for emitter resistor value? May I know the relationship between emitter resistor value and output amplitude? How about power consumption depending on emitter resistor value? I'll appreciate if you also share the useful document about this.
Best regards,
Alice
Hello Alice,
I recommend choosing an emitter resistor between 120 ohms and 240 ohms. 120 ohms is the equivalent of the 50 ohm termination to Vcc - 2 V. However if you want to save some current, you can increase the emitter resistor value. For this I often recommend 240 ohms. However 200 ohms also seems much of the same current savings.
Load is AC coupled 100 ohms differential.
| Frequeny | Format | Emitter Resistor | Amplitude Diff (Vpp) | Icc (mA) | Informational Only |
| 122.88 | LVPECL16 | 68 ohm | 1.55 | Yes | |
| 122.88 | LVPECL20 | 68 ohm | 1.92 | Yes | |
| 122.88 | LCPECL | 68 ohm | 1.8 | Yes | |
| 122.88 | LVPECL16 | 120 ohm | 1.54 | 35.5 | No |
| 122.88 | LVPECL20 | 120 ohm | 1.85 | 36.2 | No |
| 122.88 | LCPECL | 120 ohm | 1.45 | 27.3 | No |
| 122.88 | LVPECL16 | 200 ohm | 24.9 | No | |
| 122.88 | LVPECL20 | 200 ohm | 25.7 | No | |
| 122.88 | LCPECL | 200 ohm | 20.0 | No | |
| 122.88 | LVPECL16 | 240 ohm | 1.25 | 22.1 | No |
| 122.88 | LVPECL20 | 240 ohm | 1.24 | 22.9 | No |
| 122.88 | LCPECL | 240 ohm | 0.968 | 18.0 | No |
| 122.88 | LVPECL16 | 330 ohm | 1.04 | ||
| 122.88 | LVPECL20 | 330 ohm | 1.04 | ||
| 122.88 | LCPECL | 330 ohm | 0.761 |
73,
Timothy
