| ??? 02/25/06 13:47 Read: times |
#110780 - Aha! Responding to: ???'s previous message |
I am basically using this network as a level shifter, i.e. to drop a signal from 15V to 4.7V. That is why I am not using the 7805. Sorry, I misunderstood you all the time. I thought that you want to supply the TTL-chip. Well, level shifting can be done by using a zener or a resistive voltage divider, but due to the rather high input low current (IIL) of 1.6mA of TTL-chip, value(s) of resistor(s) must be very small. It's much better to use an additional transistor stage for this level shifting or to use a HCMOS-chip instead of TTL-chip. Level shifting for HCMOS-chips is much easier. Kai |
| Topic | Author | Date |
| Zener Turn-on-time | 01/01/70 00:00 | |
| Remedy | 01/01/70 00:00 | |
| Thank You Kai | 01/01/70 00:00 | |
| Divider | 01/01/70 00:00 | |
| Resistor values | 01/01/70 00:00 | |
| Read again my calculation example | 01/01/70 00:00 | |
| drop that stupid resistor to ground | 01/01/70 00:00 | |
| can you draw the schematic? | 01/01/70 00:00 | |
| Assistance required to post Sch | 01/01/70 00:00 | |
| If using "Windows" | 01/01/70 00:00 | |
| Typo Oops | 01/01/70 00:00 | |
| Using a cap is enough | 01/01/70 00:00 | |
| actually for the "typical" use it is not | 01/01/70 00:00 | |
| Less than 1nsec | 01/01/70 00:00 | |
| Resistor instead of the cap | 01/01/70 00:00 | |
| Sch | 01/01/70 00:00 | |
| ALWAYS design to worst case. | 01/01/70 00:00 | |
| Homepage | 01/01/70 00:00 | |
| why is that 1k still there | 01/01/70 00:00 | |
| Aha! | 01/01/70 00:00 | |
Thank you all for your help. | 01/01/70 00:00 |