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Everything posted by walid

  1. Thank you Hero999, you helped me Like this circuit? Another question: Why the transmitter frequency change when the battery goes down, despite that the calculation of LC tank frequency does not doesn't take the value of the battery into account? thank you alot
  2. hi please look at the following circuit, the author claim it is AM transmitter: it is from: http://www.zen22142.zen.co.uk/Circuits/rf/amtx.htm it is look exactly FM Transmitter, the only difference is in the values of capacitors and coils!!! Is there another difference I did not watch? Are both circuits were the same? thanks alot.
  3. Please i didn't understand. what if we use a buffer circuit between? thank you KevinIV
  4. Hi when you build a FM transmitter with LC tank circuit the frequency is: f = 1/(2 pi square root LC) why then when battary goes down the frequency is altered in the receiver? thanks
  5. Like this: http://www.talkingelectronics.com/projects/27MHz%20Transmitters/27MHzLinks-1.html i understand you the reciever sense the carriar if ther is a cariar it do somthing like moving forward if no carriar do somthing else. thank you guru
  6. Thank you guru it is good and fast answer Now you this is only an oscillator niether AM nor FM what you think it used for? thank you guru
  7. Is this circuit using a hartely osc.? if yes please answer these questions: 1- is the emitter resistor affect the frequency of oscillation? 2- this is a transmitter circuit, is it FM or AM and why? thank you very much.
  8. Hi when i want to design a preamplifier using BJT and need to have a maximum symetrical voltage swing at the output, then two conditions must be satisfied: 1- VCE = 0.5 VCC 2- I (saturation) = 2 IC Is there other conditions must be taken into acount?
  9. Hello When one design preamplifier using BJT voltage-divider unbupassed Emitter config, one want max symetrical signal swing at the collector. To do this, VCE = 0.5 VCC & I (saturation) = 2 IC = VCC/(RC+RE) If I want a voltage gain = A, then A= RC/(RE+re), where re = 0.026/IE, so RC = A(RE+re) --------------(eq.1) as said before, for max symetrical signal swing at the collector, 2 IC = VCC/(RC+RE) ==> RC = (VCC/2IC) - RE ------(eq.2) From (eq.1) & (eq.2) we get: A(RE+re)= (VCC/2IC) - RE, solvig for RE yields: RE = {VCC/2(1+A)IC} - (A/A+1)re question #1: Is there any error in either equations or concepts If yes, corrected me, please
  10. Whick R Rs , Zin or both if both, in parallel or sereise?? thank you
  11. Hello I built an audio amplifier that has an input impedance of 12k ohm my source signal was 1 mV and internal resistance Rs=1.2K ohm what the suitable value of the capacitor that must be inserted between? thanks alot.
  12. Hi I need a circuit that when the upper signal is in, get the out signal at the output thank you if the phoito is not appear. the input sirnal is a dc positive pulses and the needed output is dc contenuous
  13. Hello Q1) If the received signal frequency = 100 MHz, then the local oscillator equal 110.7 or 89.3 MHz? thanks
  14. If the cutoff frequency of both filters is not the same? is it sitll -6dB thanks
  15. Are you mean like emitter follower? What about a voltage divider configuration preamp. is there a situation here that we want a high IC current? I stay, think long time about it, choosing small current (IC) give us a high Zin a long batt life and a transistor works in light duty, why not choose a very small current like 0.1 mA or even 10 uA, i know that big resistors will be used but this is no broblem! thanks alot.
  16. Hello everyone We all know that Input Impedance decreased when we choose a high collector current, and that is ok I want to ask: When one choose high current? thank you
  17. Hi for the LPF shown below, the cuoff frequency is at -3dB or -6dB and why? thanks
  18. Hi If you read the discussion in the following link will return you the great benefit http://www.electronics-lab.com/forum/index.php?topic=4705.0
  19. Thank you guru I really miss you
  20. Hi Why an Electrolytic Capacitor explode when connected in reverse mannar? thank you
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