I am trying to design a Widlar current source to drive an RC circuit/IC 555 timer. I am having some trouble simulating the current source correctly. I am using LTSpice IV and I am using their 2N2907 transistor model. I have checked my calculations twice, but the Simulated Vbe is too high and the currents are all in pico amps where they should be in milliamps. Any help would be appreciated.

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  • 2
    \$\begingroup\$ Is one of those transistors upside-down? \$\endgroup\$ Mar 7 '17 at 6:22
  • \$\begingroup\$ Thank you for pointing this out, I fixed that, but the simulation still isn't giving me any of the expected values \$\endgroup\$ Mar 7 '17 at 21:59
  • \$\begingroup\$ The transistors should be NPN, not PNP. \$\endgroup\$
    – bobflux
    Mar 7 '17 at 22:13
  • \$\begingroup\$ Or you could have reversed the battery... \$\endgroup\$ Mar 7 '17 at 22:38

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