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Generator on a BFxxx transistor with an output of 5V amplitude.

Prodig 4954 7
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  • #1 4550197
    Prodig
    Level 20  
    Warm welcome.

    I need to make an LC generator with a frequency of about 3MHz on some BFxxx transistor. I want the sine wave range to be from about 0 to about 5V with a 5V supply. Simply put, I want to measure this frequency with an ATMEGA.

    I found something like this: http://www.sklep.avt.com.pl/photo/_pdf/AVT119.pdf
    Would the FM generator part (obviously I won't be using modulation) made on a BF200 be suitable?

    By the way, I will also ask about some simple program for calculating coil parameters.

    Greetings.
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  • #3 4550459
    Prodig
    Level 20  
    I have corrected the link above.
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  • #4 4550546
    Jerzy Węglorz
    Level 39  
    I would rather suggest a generator on TTL bones, or TTL-LS, then you have NEARLY 5V! Check this out:
    Generator on a BFxxx transistor with an output of 5V amplitude. .
    Instead of C you can put in a quartz, or a WIDE LC circuit, also works nicely ....
  • #5 4550833
    161MDS01
    Level 24  
    Jerzy Węglorz wrote:
    I would rather suggest a generator on TTL bones, or TTL-LS, then you have NEARLY 5V! Check this out:
    Generator on a BFxxx transistor with an output of 5V amplitude. .
    Instead of C you can put in a quartz, or a WIDE LC circuit, also works nicely ...


    Buddy George from what I read in Prodig's post he needs a sine wave not a rectangle and this generator will output a pure rectangle as for the stabilisation of this generator hmm I have read a bit about it and some people are not happy with it...Kudos to you





    Daniel
  • #6 4550838
    M. S.
    Level 34  
    The circuit from the link is good. For 3MHz you would need to increase the capacitors between base and emitter and emitter and ground to about 100pF. The signal is taken off the emitter. You can increase its amplitude by increasing the supply voltage (and the emitter resistor). You can also add an amplifier on a transistor, which when overdriven (at such low frequencies) will shape a waveform close to a rectangle.
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  • #7 4550852
    Jerzy Węglorz
    Level 39  
    If the signal input is on an Atmega, the best accepted waveform is rectangular, with TTL levels.
  • #8 4550963
    Prodig
    Level 20  
    Thank you for your answers. Indeed, a circuit with gates is rather out. The Atmega can handle a sine wave - it is important that the sine wave has values varying from 0 to 5V.
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Topic summary

The discussion revolves around designing an LC generator using a BFxxx transistor to achieve a sine wave output of approximately 5V amplitude at a frequency of 3MHz. The original poster inquires about the suitability of a circuit from a provided link, specifically mentioning the BF200 transistor. Responses suggest that while the linked circuit may work, adjustments such as increasing capacitor values are necessary for the desired frequency. Some participants recommend using TTL logic for generating signals, noting that the ATmega can handle sine waves as long as they stay within the 0 to 5V range. Additional resources for coil parameter calculations are also shared.
Summary generated by the language model.
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