Anyone use output stage like this

deleveld · 19th January 2005, 02:26 PM

Hi Everyone...

Has anyone ever seen an output stage like this being used for audio? I believe output stages like this are sometimes used for motor control circuits. I'm trying to design an amp using it and am having problems balancing the two outputs....

http://www.deleveld.dds.nl/outstage.jpg

Thanks,

Doug Eleveld

Charles Hansen · 19th January 2005, 04:06 PM

This circuit is designed to turn the motor fully on in one of two polarities. This is not what you want to do for audio, and it is not surprising that you are having troubles.

Many amps have been made with a balanced bridge output. You are probably better off using common collector output devices instead of common emitter. One example of a balanced bridge output amplifier can be found at:

http://www.diyaudio.com/forums/attac...amp=1077770119

Good luck!

djk · 20th January 2005, 11:52 AM

For audio?

Does a siren driver count?

Your circuit is the same as the Zetex siren driver, rail to rail square wave.

Go to:

http://home.kimo.com.tw/skychutw/

Then click on:

Circuits, and then:

Liquid-Coopled Power Amplifier (Wireless Word, Dec. 1974, p505~507)

deleveld · 20th January 2005, 01:08 PM

Huh? The same?

The output stage i showed is VERY different then the one you showed. Yours uses output devices in a complementary-darlington with the drivers with 4 drivers and 4 output devices. My drivers are normal darlington with the bottom drivers but complementary to the top drivers and shares 2 drivers for 4 output devices.

Doug

DRC · 20th January 2005, 02:25 PM

Doug,
Is your problem differential offset ? I would guess component tolerance / Vbe temperature dependency combined with voltage gain (x16 ?) are the cause. The obvious solution would be some feedback, a servo or both (unless you are trying to avoid that) …

Also, I think your bias conditions are dependant on the common mode input voltage.

dave

djk · 20th January 2005, 07:36 PM

SInce you have trouble with English I will try again.

Your circuit is the same as a ZETEX siren driver circuit, they make square waves and are generally driven from batteries and need rail to rail operation.

http://lib1.store.vip.sc5.yahoo.com/...ics/kit116.pdf

The circuit I linked to is an amplifier with a DC off-set control and the X feedback scheme favored by Nelson Pass. It may be built with EF or CFP output pairs.

The Hadley 622 at the Skychu site is also another nice bridge amp with the X feedback and has current limiting, DC offset adjust and bias shown.

The original Sumo Andromeda is a BJT version of Charles' FET bridge, but only the FET version is at the Sky site.

The Ampzilla III is a forerunner of the Sumo, it is at the Sky site too.

19th January 2005, 02:26 PM	#1
deleveld diyAudio Member Join Date: Apr 2002	Anyone use output stage like this Hi Everyone... Has anyone ever seen an output stage like this being used for audio? I believe output stages like this are sometimes used for motor control circuits. I'm trying to design an amp using it and am having problems balancing the two outputs.... http://www.deleveld.dds.nl/outstage.jpg Thanks, Doug Eleveld

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19th January 2005, 04:06 PM	#2
Charles Hansen diyAudio Member Join Date: May 2003 Location: Colorado	This circuit is designed to turn the motor fully on in one of two polarities. This is not what you want to do for audio, and it is not surprising that you are having troubles. Many amps have been made with a balanced bridge output. You are probably better off using common collector output devices instead of common emitter. One example of a balanced bridge output amplifier can be found at: http://www.diyaudio.com/forums/attac...amp=1077770119 Good luck!

20th January 2005, 11:52 AM	#3
djk diyAudio Member Join Date: Feb 2001 Location: USA	For audio? Does a siren driver count? Your circuit is the same as the Zetex siren driver, rail to rail square wave. Go to: http://home.kimo.com.tw/skychutw/ Then click on: Circuits, and then: Liquid-Coopled Power Amplifier (Wireless Word, Dec. 1974, p505~507)

20th January 2005, 01:08 PM	#4
deleveld diyAudio Member Join Date: Apr 2002	Huh? The same? The output stage i showed is VERY different then the one you showed. Yours uses output devices in a complementary-darlington with the drivers with 4 drivers and 4 output devices. My drivers are normal darlington with the bottom drivers but complementary to the top drivers and shares 2 drivers for 4 output devices. Doug

20th January 2005, 02:25 PM	#5
DRC diyAudio Member Join Date: Jan 2003 Location: UK (south west)	Doug, Is your problem differential offset ? I would guess component tolerance / Vbe temperature dependency combined with voltage gain (x16 ?) are the cause. The obvious solution would be some feedback, a servo or both (unless you are trying to avoid that) … Also, I think your bias conditions are dependant on the common mode input voltage. dave

20th January 2005, 07:36 PM	#6
djk diyAudio Member Join Date: Feb 2001 Location: USA	SInce you have trouble with English I will try again. Your circuit is the same as a ZETEX siren driver circuit, they make square waves and are generally driven from batteries and need rail to rail operation. http://lib1.store.vip.sc5.yahoo.com/...ics/kit116.pdf The circuit I linked to is an amplifier with a DC off-set control and the X feedback scheme favored by Nelson Pass. It may be built with EF or CFP output pairs. The Hadley 622 at the Skychu site is also another nice bridge amp with the X feedback and has current limiting, DC offset adjust and bias shown. The original Sumo Andromeda is a BJT version of Charles' FET bridge, but only the FET version is at the Sky site. The Ampzilla III is a forerunner of the Sumo, it is at the Sky site too.

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