AK5385A ADC Overflow indicator

[Andy Peters]

The issue with the transistor turning off too slow is because it is operating in base current amplification mode to multiply that base current to drive the collector load. Instead driving the base with a voltage (fraction of the cap voltage divided down) will cause the current to drop more quickly (exponentially) between full on at say .7 and full off at say .4V

The really clever solution is to write the slowly dimming LED into the marketing spec so it becomes a feature instead of a fault.

I think the slowly-dimming peak LED looks pretty cool!

-a

 

[Rochey]

I agree. It's all a question of tuning the decay to taste

 

[Moby]

The issue with the transistor turning off too slow is because it is operating in base current amplification mode to multiply that base current to drive the collector load. Instead driving the base with a voltage (fraction of the cap voltage divided down) will cause the current to drop more quickly (exponentially) between full on at say .7 and full off at say .4V

The really clever solution is to write the slowly dimming LED into the marketing spec so it becomes a feature instead of a fault.

I think the slowly-dimming peak LED looks pretty cool!

-a

Agree, slowly dimming Led is a matter of taste. I would like to have sharp decay Instead of one transistor I tried this (in sim) old school One-shot Monostable Multivibrator . The question is did I trimmed all values correctly?