I was experimenting with this circuit for inverting RS232 signals:
Transistor: BC546. Diode: 1N4148.
It worked fine when feeding in ±5V, but testing with ±10V it stopped working and the transistor was destroyed.
I suspect either:
- It is bad if the base voltage exceeds the collector voltage
- I exceeded the emitter-base voltage (the maximum being 6V)
What do you think?
If I am right, I thought of perhaps:
- A 5V zener diode in parallel with the other diode to clamp the input voltage to 5V
- Another normal diode between Base and Collector (or Base and +5V) to clamp the input voltage to the collector voltage
What would you recommend?