i need to switch the transitor (Vce minimal) when input voltage (0 - 18V) is greater than 6.3V. To achieve sharp edge I use a zener diode D1. However, I also need a protect transistor base, so I use a protecting diode D2.
I run into the problem, when D2 needs a high current, but i cannot load the input voltage devider in that way due to destroying the sharp edge so I use a 4.7K.
How to solve the clamping diode D2?
The characteristic should be sharp at least like this:
I tried to change R2 from 4K7 to 1K (to maintain D2 zener current)and it seems the sharpness stay there.
Any idea how to solve this circuit better?
To make it clarify, it will be used in circuit below. It is current limiter with, let say Mosfet protection. In case The Vds is higher than 5V, the mosfet will turn on completely, so it acts like fuse.
Due to this no need to precise comparator (4.5 or 5.5V doesnt matter).
If someone see improvements in schematic, please correct me.