Is the ideal output impedance of a Wilson Current Mirror 0?

Also, in the formula for the actual output impedance of Wilson Current Formula (i.e. R_out = [B/2]* r_o), what does r_o stand for? Also, what is the order of magnitude of a Wilson Current Mirror?

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  • \$\begingroup\$ \$r_o\$ represents the small-signal output resistance defined by the early voltage and the collector current. \$\endgroup\$ – KingDuken Mar 16 '18 at 2:18
  • \$\begingroup\$ Think about it - ideally, it would have infinite output impedance, so no matter what load you attached to, the total impedance (and therefore current) would still be the same. Infinite + Load ≈ Infinite, so your current remains unchanged. \$\endgroup\$ – DSWG Sep 12 '18 at 0:37

The mirror like an ideal current source has infinite impedance except for the leakage r_o due to the Early Effect and Beta, B


Order of magnitude for current depends on the device Imax, Pmax and gain matching

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  • 1
    \$\begingroup\$ I recall building a Wilson current mirror out of discretes, with emitter swamping resistors. The Rout was 5 Million ohms, running at 10mA, measured on a Fairchild curve tracer. \$\endgroup\$ – analogsystemsrf Mar 16 '18 at 3:27

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