Open collector npn output

marjan · 14th January 2005, 01:21 PM

Can someone give a brife explanation and maybe some example (shema) of npn open collector output stage in audio amp?
marijan

richie00boy · 14th January 2005, 01:49 PM

I would have thought that this would only apply to a switching circuit, e.g. comparator, as it is capable only of sinking current not sourcing.

Enzo · 15th January 2005, 08:29 AM

I guess you could do some sort of single ended thing, but why on earth would one want to?

A little more info on your intent or application maybe?

marijan · 15th January 2005, 02:58 PM

I simply can not understand how can npn output stage of an amplifier work without electrical conection (at least I`m not able to determine it using multimeter) from 1 (out of 4) transistor collectors to the rest of the circuit. But mesuring of the voltage (in working set up-sorce and loade on) show`s -45V on colector on that npn.

Marijan

richie00boy · 15th January 2005, 05:20 PM

Ahh, now I see. It's very simple

Basically, the other three transistors are doing the work so the amplifier will appear to be fine until you stress it. You are seeing -45V on the one transistor that is unconnected simply because it's emitter is connected to the -ve rail and the device is turning on = low resistance.

marijan · 15th January 2005, 07:40 PM

Thanks Richie. I draw a quick skatch but I`m not shure, does it make any sense. All npn`s out.

14th January 2005, 01:21 PM	#1
marjan diyAudio Member Join Date: Jul 2002 Location: slovenija	Open collector npn output Can someone give a brife explanation and maybe some example (shema) of npn open collector output stage in audio amp? marijan

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14th January 2005, 01:49 PM	#2
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	I would have thought that this would only apply to a switching circuit, e.g. comparator, as it is capable only of sinking current not sourcing.

15th January 2005, 08:29 AM	#3
Enzo diyAudio Member Join Date: Sep 2004 Location: Lansing, Michigan	I guess you could do some sort of single ended thing, but why on earth would one want to? A little more info on your intent or application maybe?

15th January 2005, 02:58 PM	#4
marijan diyAudio Member Join Date: Jul 2002 Location: Slovenija	I simply can not understand how can npn output stage of an amplifier work without electrical conection (at least I`m not able to determine it using multimeter) from 1 (out of 4) transistor collectors to the rest of the circuit. But mesuring of the voltage (in working set up-sorce and loade on) show`s -45V on colector on that npn. Marijan

15th January 2005, 05:20 PM	#5
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	Ahh, now I see. It's very simple Basically, the other three transistors are doing the work so the amplifier will appear to be fine until you stress it. You are seeing -45V on the one transistor that is unconnected simply because it's emitter is connected to the -ve rail and the device is turning on = low resistance.

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