All PNP BJT has low HFE
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pberna 1 week ago
Dear All Simulating a simple current limiter I've noticed that the PNP BJT are simulating with a very low Hfe (around 4) but it should be much higher For example the 2N3906 should have 100 as Hfe ![image.png](//image.easyeda.com/pullimage/9HuqA6f9m4shDWE5IpkGdUGJklh67VU2Ed7EZi2z.png) <br> Operating Point Simulation results: V(volprobe3):                 2.524861336995146e+000V       voltage V(volprobe2):                 1.823509493571086e+000V       voltage V(volprobe1):                 3.242935620221527e+000V       voltage Circuit: \*\* Sheet\_1 \*\* Direct Newton iteration for .op point succeeded. Semiconductor Device Operating Points:                         --- Bipolar Transistors --- Name:       q2          q1 Model:    2n3906      2n3906 Ib:      -1.15e-03    6.41e-13 Ic:       5.71e-03    1.60e-13 Vbe:      7.01e-01    7.18e-01 Vbc:     -7.18e-01   -5.71e-02 Vce:      1.42e+00    7.75e-01 BetaDC:  -4.97e+00    2.49e-01 Gm:      -1.76e-01   -3.51e-12 Rpi:      1.00e+12    1.00e+12 Rx:       2.00e+01    2.00e+01 Ro:       5.67e+00    2.85e+11 Cbe:      8.00e-12    8.01e-12 Cbc:      4.44e-08    4.62e-12 Cjs:      0.00e+00    0.00e+00 BetaAC:  -1.76e+11   -3.51e+00 Cbx:      0.00e+00    0.00e+00 Ft:       6.32e+05    4.24e-02 <br> <br> Date: Tue Apr 06 20:03:23 2021 Total elapsed time: 0.015 seconds. tnom = 27 temp = 27 method = trap totiter = 8 traniter = 0 tranpoints = 0 accept = 0 rejected = 0 matrix size = 11 fillins = 4 solver = Normal Matrix Compiler1: 1.04 KB object code size Matrix Compiler2: 1.01 KB object code size Powered by LTspice <br> Any idea ?
andyfierman 1 week ago
For the moment, until the 2N3906 symbol in the System library is fixed (collector and emitter spice pins have been reversed: an error report has been submitted), please replace the 2N3906 transistors that you have used with this one from the User Contributed Library: ![image.png](//image.easyeda.com/pullimage/rH48r0nusxo3yPS3fb5u6S3hC8zjUxlD7TBomty2.png) * In future, when asking for help on a simulation prtoject, please post the URL to a public copy that demonstartes the issue. <br> <br>
pberna 1 week ago
Thanks! I see the same error for other PNP trransistor [https://easyeda.com/editor#mode=sim,id=6c75836ea95340a898346156a325d8a3](https://easyeda.com/editor#mode=sim,id=6c75836ea95340a898346156a325d8a3)<br> <br>
andyfierman 1 week ago