I'm trying to build a 9V battery tester with zener diodes.
I am doing tests with a adjustable power supply.
With a 3904 transistor to do the switching it works ok.
But one problem that I have is that the LED is fading on too slowly.
In this schematic it starts glowing at 9.2V and is fully on at about 10V.

How would I achieve a sharper switching, like the led is fully lit at 9.2V and fully off at 9.1V?
The 3904 already has a high gain.
But maybe I can use a different transistor zu achieve this?
 

^{simulate this circuit – Schematic created using CircuitLab}

I'm trying to build a 9V battery tester with Zener diodes. I am doing tests with an adjustable power supply.

With a 3904 transistor to do the switching it works ok, but the LED is fading on too slowly.

In this schematic it starts glowing at 9.2V and is fully on at about 10V.

How would I achieve a sharper switching, like the LED is fully lit at 9.2V and fully off at 9.1V?

The 3904 already has a high gain, but maybe I can use a different transistor to achieve this?

^{simulate this circuit – Schematic created using CircuitLab}