Operation Characteristics of a 3055T Device

Assuming the device is good, .....Yes leakage current. But you need to show your test circuit, as this may be a trick question, as ground on the base is "none" voltage.

Basically, I'm involved with a friends non-working DIY power supply.

What prompted the question is my non-familiaruty with the 3055T device.

In researching one of the problems he lifted the base that was connected to an LM 723 IC and powered up the power supply.

26.2 VDC is connected to the collector and the emitter is connected to two 3055 transistor bases, in parallel, with their collectors connected to this same 26.2 VDC line.

Each of these collectors have .1 Ohm 10 watt resistors preceding the parallel junction.

Now, you have it. The 3055T base has been disconnected from the IC and a voltage is being read on its collector.

According to a spec sheet there needs to be 1.8 VDC between collector and base, in order to turn on this transistor.

Please advise.

O.K., Thanks -

You've answered my inquiry and the the pass transistor combind output is being held to a preset value via the 723 IC and VR network at pin 4. i.e. 13.8 VDC

Have a great week!

Thanks for your additional information.

I appreciate your taking the time to enlighten me concerning NPN transistors.

Have a great day.

Here's a data sheet. The collector cutoff current is 700μa @ 30V. I forgot to mention that if you put more than 60V on the collector, you will get a whole lot more current as the base-collector junction breaks down.

http://hep.fi.infn.it/PAMELA/pdf/MJE3055.pdf

Thanks, again, for your helpful information.

MidnightCowboy:


Very much yes. Leaving the base open is very dangerous. It reduces the collector - emitter breakdown potential. Better to tie it to ground using some resistor like 10K to 100K ohms.

Lifting the base from the 723 IC was on of short duration, in order to determine the effect on paired NPN output.

MidnightCowboy:

Most of the amplifiers were very sensitive to their non-inverting input being floated and often were damaged. Only those amplifiers that are protected against such open circuit will survive.

For transistors, it is often specified that open base brings down the operating voltage of the transistors also. Some minimum base charge drainage circuit is essential. In Avalanche mode, charge injection between collector emitter is often limited else junction will get punctured permanently.

Thank you for your learned opinion.

I appreciate your taking the time to pass this information on to me!