# Measuring impedance

#### n9xv

Joined Jan 18, 2005
329
I'am looking for the verbage stating the principle of measuring output impedance of an amplifier with the input terminals shorted, and, measuring the input impedance with the output terminals shorted. I use to have books explaining this method of impedance measurement but cant find it now. I think I remember the method but I cant find anything on the net covering it.

Any input?

#### Ron H

Joined Apr 14, 2005
7,014
Sounds like you are talking about y-parameters. You might also want to look into z-, s-, and h-parameters.

#### Papabravo

Joined Feb 24, 2006
13,522
Originally posted by Ron H@Jun 12 2006, 06:45 PM
Sounds like you are talking about y-parameters. You might also want to look into z-, s-, and h-parameters.
[post=17683]Quoted post[/post]​
One of the big deals about s-parameters is that they do not require outputs to be shorted to do the measurement. Shorting the output of a device presented several practical problems for y, h, and z parameters.

Measuring s-parameters

#### Ron H

Joined Apr 14, 2005
7,014
Originally posted by Papabravo@Jun 12 2006, 06:57 PM
One of the big deals about s-parameters is that they do not require outputs to be shorted to do the measurement. Shorting the output of a device presented several practical problems for y, h, and z parameters.

Measuring s-parameters
[post=17686]Quoted post[/post]​
Actually, h-parameters are the only other ones requiring that the output be shorted. Z-parameters are measured with open circuits.

#### n9xv

Joined Jan 18, 2005
329
Seems like I remember this applying to audio amps. I wish I had the equipment, at least I could try it! Good links by the way!

#### Thevenin's Planet

Joined Nov 14, 2008
183
Anticipate the New Year with convidence!
I don't know much about the S-Parameters but the information from the web site(link) the you suggested can be very useful. The original post by Papabravo says that it not neccesary to shorten and have opens but in regard to the link(Spectrum Software it is stated that inductors and capacitors are to be used to produce these shorts and opens.Also the Transistor is Biased.Data can be use to start me down a understanding route, Thanks alot fellas