1
\$\begingroup\$

How do I measure the small signal output impedance (ro) of a modified wilson current mirror?

example Q4:

enter image description here

\$\endgroup\$
  • \$\begingroup\$ Are you looking for a sophisticated Test Engineer's approach? Do you have some acceptance criteria? or just idle curiosity? \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Apr 26 at 0:21
  • \$\begingroup\$ At this point just doing some side research for a project \$\endgroup\$ – Roo Apr 26 at 0:23
  • 1
    \$\begingroup\$ If you apply a square wave to DC at V1 with a current sense resistor of suitable value, what do you expect for \$R_O = \frac{\Delta V}{\Delta I}=10^7?, 10^{10}?\$? \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Apr 26 at 0:28
  • \$\begingroup\$ I found at gain of 6.3G ohm at 1 Hz, however, it gradually decreases with frequency. I'm not sure why the resistance decreases as the frequency increases. \$\endgroup\$ – Roo Apr 26 at 0:53
  • \$\begingroup\$ What do you expect Coss to be? 1pF? 100pF? \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Apr 26 at 0:58
2
\$\begingroup\$

\$R_O = \frac{\Delta V}{\Delta I}\$

In other words, vary the output voltage and measure the corresponding change in current.

If you're asking something more subtle than that, please clarify by editing your question.

\$\endgroup\$
  • \$\begingroup\$ updated the question \$\endgroup\$ – Roo Apr 26 at 0:13
  • \$\begingroup\$ Same answer. Apply an AC voltage and measure the AC current. You can make it as large or small as you like. You can even vary the frequency. \$\endgroup\$ – Dave Tweed Apr 26 at 0:16
  • \$\begingroup\$ where is the ideal place to place the AC source? \$\endgroup\$ – Roo Apr 26 at 0:20
  • \$\begingroup\$ In series with V1. \$\endgroup\$ – Dave Tweed Apr 26 at 0:36
  • \$\begingroup\$ I found at resistance of 6.3G at 1 Hz \$\endgroup\$ – Roo Apr 26 at 0:54

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.