Output Impedance?

ble0t · 19th January 2006, 04:10 PM

How would one calculate the output impedance of something like this:

http://www.st.com/stonline/products/...73/74v1g70.pdf

Do you need to average the high and low voltages both divided by the typical output current?

Does that make any sense?

Thanks!

poobah · 19th January 2006, 04:17 PM

You need to divide a change (difference) in output voltage by a corresponding change in output current. They didn't give you the data to do this.

This is a logic device... probably not good for a linear application.

ble0t · 19th January 2006, 04:35 PM

It's not for a linear application persay. It's for buffering a digital output signal (more specifically SPDIF). I want to match an impedance for the primary side of a transformer. I can't get the output impedance of the transmitter I'm using, so I thought buffering it and using that output impedance would be the best idea.

poobah · 19th January 2006, 05:19 PM

HMMM... 25 Ohms might be a good guess for CMOS. I have calculated Zo for these device before.

Also look for "differential line (or bus) driver". They won't be lacking in spec's.

ble0t · 19th January 2006, 05:45 PM

Thanks much

19th January 2006, 04:10 PM	#1
ble0t diyAudio Member Join Date: May 2004 Location: Milwaukee, WI	Output Impedance? How would one calculate the output impedance of something like this: http://www.st.com/stonline/products/...73/74v1g70.pdf Do you need to average the high and low voltages both divided by the typical output current? Does that make any sense? Thanks! __________________ gravity always wins

19th January 2006, 04:35 PM	#3
ble0t diyAudio Member Join Date: May 2004 Location: Milwaukee, WI	It's not for a linear application persay. It's for buffering a digital output signal (more specifically SPDIF). I want to match an impedance for the primary side of a transformer. I can't get the output impedance of the transmitter I'm using, so I thought buffering it and using that output impedance would be the best idea. __________________ gravity always wins

19th January 2006, 05:45 PM	#5
ble0t diyAudio Member Join Date: May 2004 Location: Milwaukee, WI	Thanks much __________________ gravity always wins

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19th January 2006, 04:17 PM	#2
poobah diyAudio Member Join Date: Nov 2005	You need to divide a change (difference) in output voltage by a corresponding change in output current. They didn't give you the data to do this. This is a logic device... probably not good for a linear application.

19th January 2006, 05:19 PM	#4
poobah diyAudio Member Join Date: Nov 2005	HMMM... 25 Ohms might be a good guess for CMOS. I have calculated Zo for these device before. Also look for "differential line (or bus) driver". They won't be lacking in spec's.

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