I'm trying to analyze an FM transmitter circuit, but it has a 2N3904 circuit. I have just basic circuit analysis tools; how could I get a circuit that does similar things to this transistor using just L's, R's, C's and sources? I know I could apply the hybrid-\$\pi\$ model, but I don't know how to get the parameters. Is not for practical purposes, so I don't care about power and frequencies concerns.

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    \$\begingroup\$ You can't. A transistor is a current amplifier. You cannot build an amplifier out of passives. \$\endgroup\$ Jun 3, 2014 at 17:05
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    \$\begingroup\$ Ostensibly, "and sources" includes the not-passive components that would be necessary. \$\endgroup\$
    – Phil Frost
    Jun 3, 2014 at 17:14
  • \$\begingroup\$ "I have just basic circuit analysis tools". Get better tools! LTSpice is free; it has a 2N3904 model. \$\endgroup\$
    – Kaz
    Jun 3, 2014 at 17:36
  • \$\begingroup\$ How do you define "basic circuit analysis tools" in a way that doesn't include a copy of LTspice or even Berkeley SPICE? Both will simulate a small-signal NPN. \$\endgroup\$ Jun 3, 2014 at 17:36
  • \$\begingroup\$ @WarrenYoung Beat you by seconds. :) Only because I didn't include a link, and mention Berkeley SPICE. :( \$\endgroup\$
    – Kaz
    Jun 3, 2014 at 17:36

1 Answer 1


One on-line source and many others have information on the 2N3904 transistor. The one I linked gives pretty good parameters for 2N3904 Hybrid -Pi model.

If you have a spice simulator, try looking for a Spice model for 2N3904.


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