Need help picking a Transistor

Discussion in 'General Technical Questions and Answers' started by WQ4G, Oct 10, 2019.

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  1. WQ4G

    WQ4G Ham Member QRZ Page

    Greetings:

    Need some Transistors for one of my victims. The existing transistors are 2n3011 and the parts list for the set calls for "SI NPN Gen. Purp TO92" and does not specify the exact transistor.

    The data for the 2n3011 is here:

    https://alltransistors.com/transistor.php?transistor=2722

    I have a few different kinds of transistors on hand and would like to use some of them if possible. For example I have quite a few MPSA05, MPSA13, and 2N2222.

    Here is the datasheet for the the MPSA05:

    https://www.onsemi.com/pub/Collateral/MPSA05-D.PDF

    Here is the datasheet for the MPSA13:

    https://www.onsemi.com/pub/Collateral/MPSA13-D.PDF

    And, the datasheet for the 2n2222:

    https://www.electroschematics.com/wp-content/uploads/2009/04/2n2222-datasheet.pdf

    It appears to me that these transistors (except for possibly the MPSA05 due to the 4 volt emitter-base voltage spec) would all be sufficient for the voltages and currents. But, none of them are specified 'General Purpose.' And the MPSA13 are Darlington Transistors. The transistors will be used in the RF chain AFTER the (1st) RF Amplifier as Mixer, First IF Amp, 2nd IF Amp, Low Oscillator, Squelch Gate, etc.

    Anyone chiming in with additional information would be greatly appreciated... Which, if any of those Transistors would qualify, or be a good substitute, as general purpose Transistors?

    Thanks

    Dan WQ4G
     
  2. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    The 2n2222 is as general purpose as they come! :)
     
    NE1U, WQ4G, KD2ACO and 2 others like this.
  3. W9WQA

    W9WQA Ham Member QRZ Page

    dont know your circuit but i like to have a bag full of 3904 and 3906 around for small transistors!
    they work from audio,switching, to vhf
     
    K8AI and N0TZU like this.
  4. WA7ARK

    WA7ARK Ham Member QRZ Page

    2n3904
     
    NE1U likes this.
  5. AG6QR

    AG6QR Subscriber QRZ Page

    Any time I've heard the phrase "general purpose NPN transistor", it has always meant 2n2222 or 2n3904, whichever you happen to have more of in your parts bin at the moment.
     
    KK4NSF, WQ4G, AC0OB and 1 other person like this.
  6. KA9JLM

    KA9JLM Ham Member QRZ Page

    Keep the gain figure close to original.

    Forward Current Transfer Ratio (hFE), MIN: 30
     
  7. AG6QR

    AG6QR Subscriber QRZ Page

    Better yet, use feedback in the circuit to make it work well over a wide range of gain figures. hFE is not closely controlled in typical manufacturing processes, and most data sheets only specify a guaranteed minimum, allowing any part with at least that much gain to pass inspection and be sold to customers.

    If your circuit relies on a particular value of hFE, it isn't likely to work well when assembled with off-the-shelf transistors.
     
    KA0HCP likes this.
  8. W9WQA

    W9WQA Ham Member QRZ Page

    as usual, too much worrying goin on here!! just stick one in and see what happens...
     
    K8AI, K2XT, NN4RH and 3 others like this.
  9. KA9JLM

    KA9JLM Ham Member QRZ Page

    Yep. It depends on the circuit.

    I have seen some transistors that are "To Good".

    Direct couple amplifiers are fun. When one blows, They all blow.
     
  10. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    That's our specialty! :p

    In the recording studio we say, "Microphones suck and speakers blow!"
     
    KA9JLM likes this.

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