maximum Emiter Base voltage in a Bistable multivibrator circuit

[wanna_eat_1kg_of_elecons]

Hello i have made the following cicuit:

https://upload.wikimedia.org/wikipedia/commons/9/98/Transistor_Bistable.svg

R1 = R2 = 1K
R3 = R4 = 10k

The datasheet states that the maximum Emitter base voltage may be 6V

V+ = 6.3V


(1)
when i measure between R2 and R4 i measure a voltage of 5.7V. Does this mean that i am save with the max. Emitter-Base voltage?


(2)
Do they mean the emitter may be 6 V higher than the base or,
do they mean the base may be 6V higher than the emitter?

thanks for the help!!

 

[alec_t]

(1) Perfectly safe.
(2) They mean the set/reset pulses applied to the base must not take the base voltage lower than minus 6V (i.e. 6V below the emitter voltage, which is at 0V), to prevent breakdown of the base-emitter junction.

 

[Nigel Goodwin]

As your file is in some weird format I can't open it, but as long as your supply is only 6V, you should be OK - increasing it to 9V (without taking precautions) will blow the transistors (reverse Vbe breakdown).

The Vbe spec means the emitter may NOT be more than that higher than the base - or it dies.

 

[wanna_eat_1kg_of_elecons]

@nigel Goodwin


It is a picture from wikipedia here is the main page:

http://en.wikipedia.org/wiki/Multivibrator

it is the picture named: "Bistable multivibrator circuit"

Found an other picture here:
**broken link removed**
i use a 10K and not a 15K.

 

[wanna_eat_1kg_of_elecons]

(1) Perfectly safe.
(2) They mean the set/reset pulses applied to the base must not take the base voltage lower than minus 6V (i.e. 6V below the emitter voltage, which is at 0V), to prevent breakdown of the base-emitter junction.

So lets see if i fully understand. If i make the base more than 6v lower than the emitter the transistor will die. But if i make the voltage on the base 6 or more volt higher than the emitter the transistor will stay alive?

 

[alec_t]

If i make the base more than 6v lower than the emitter the transistor will die

Probably, unless any breakdown current is limited in some way.

But if i make the voltage on the base 6 or more volt higher than the emitter the transistor will stay alive?

No, it will die. If the base-emitter junction is forward-biased via a current-limiting resistor (i.e. 6V is applied to the base via R3 or R4 in your bistable circuit) the base voltage will automatically be about 0.6V. If you directly connect 6V (not current-limited) to the base the junction will burn out.

 

[audioguru]

The bistable multivibrater circuit has no coupling capacitors so the base never goes to a negative voltage. The set and reset signals float for no action or are grounded to be active.