Search results

Search Forums New Posts
  1. walid1

    preamp op amp circuit question

    very good guru, u r really a professor but please is this with the reverse of the figure and the 10u farad cap why? thanks
  2. walid1

    a very simple FM Tx

    Hi guru I go to google and search for LC Resonance and one of them was: http://www.pronine.ca/lcf.htm It is a calculator substitute L=330n and C=6.7p u will have f=106 MHz and Zo=220 ohm as i calculate it, it is not nearly infinite ohms It is very important to me to correctly calc the o/p Z of...
  3. walid1

    preamp op amp circuit question

    Hi aProgrammer thank u for fast reply Yes I agree, there are a mistake, the + and - inputs are inverted If they are Av = 1 + (R2/R1) but why they connect the (+) i/p  [the -ve in the figure] to adivider that half of VCC applied to it, why not simply connect R4 to ground and omit R3? thanks...
  4. walid1

    a very simple FM Tx

    Hi guru lets do it again at 106MHz, L =330nH  and C=6.8pf, we have XL = 2 pi f L = 220 ohm XC= 1/(2 pi f C) = 220 ohm  (resonance) Ztot = (XL*XC)/(XL+XC) = 110 ohm I think it is wrong calc, Ztot must be zero because XL = j w L and XC = -1/j w c I don't know what to do............ IF the...
  5. walid1

    preamp op amp circuit question

    Hi For the circuit shown below I want: to calculate the o/p gain to know what the function of C1 I noticed that there are something strange in it, the feedback is connected to the noninverting i/p and the voltage divider to the inverting i/p thank u in advance
  6. walid1

    a very simple FM Tx

    Hi guru First thank u for the figures from which i can see that the 1 nF has no resonable effect at AF. but u may not see this question I agree that it is complicated to calculate how much is the output voltage and current, lets assume them and investigate the tapping effect on them: If the...
  7. walid1

    a very simple FM Tx

    Hi guru This is good, but I want to introduce the effect of the 1nF cap on the lower 47Kohm. The reactance of that cap at freqs from 300Hz t0 15Khz is 10.6 Kohm to 53 Kohm 47K // 10.6K  = 8.65 K, and 47K // 53K = 24.9K so VB is not constant at VB = 9 * 47/(47+47) = 4.5v as i was think it is...
  8. walid1

    BJT biasing formulas

    Good evening Guru Thank u for fast and good reply Now I'll not ask you about filters and the -3dB, I'll postpone this to another discussion, but I noticed that C1 and the other Rs are not intended as a filter. You choosed C1 as the smallest possible cap  to couple the two parts of the circuit...
  9. walid1

    BJT biasing formulas

    Hi guru u enlarge the discussion and introduce a new aspects -at least foe me- and i can
  10. walid1

    a high pass filter question

    Thank you guru it is evident and good answer
  11. walid1

    BJT biasing formulas

    Hi guru please look at the Fig below. It is thr first stage of your FM TX I omit C2 to make it more simple to discuss Where is the Negative feedback in your circuit (below) please put some examples to a current source and bootstrapping and how they connected to collector you guru add a CE to...
  12. walid1

    BJT biasing formulas

    Hi I said before, at 12/6/2006 that: today I'll discuss with audioguru and you, the effect of adding a bypass cap to RE, its name is CE Till now we can design a perfect voltage divider BJT transistor configuration without CE When adding this CE, two circuit parameters are changes: (1) The...
  13. walid1

    a high pass filter question

    Hi when we come to design a high pass filter like that formed between stages Here C is the coupling cap and R is the i/p impedance of the next stage the cutoff freq = 1/(2 pi R C) To make the cutoff freq = say 100 Hz, u can: take C = 10 uF and R = 160 ohm OR take C = 1 uF and R = 1.6 Kohm You...
  14. walid1

    Audioguru FM Tx

    Hi guru yes exactly, i noticed this. I'll redesign it after your help, and with u makeing its range more. I know that this circuit is not better than yours, but I have a chance with this. when I build a circuit and didn't work it is more easy to me to build anthother new one than searching for...
  15. walid1

    Audioguru FM Tx

    Hi guru I build this circuit: I followed exactly their instructions I put parts very close to each other and very close to the board it work fine i built it in aboard with holes, and its area was 15 holes X 5 holes, it is very small and crowded with parts i put it in my hand, so i toutch every...
  16. walid1

    Audioguru FM Tx

    Hi guru for the circuit shown below, someone ask my the following question: Can I increase the range of this transmitter by using power transistor like BLY89 and decreasing the RE? I attached the datasheets of BLY89 i look at that datasheets and see it max freq = 175 MHz i think it can handle...
  17. walid1

    Audioguru FM Tx

    Hi guru please read the following: "The sensitivity of the WASP depends to a large extent on the value of the load resistor on the electret microphone. We have used 39k in the project, as the microphone we supply is a very sensitive type. If you wish to increase the sensitivity to super...
  18. walid1

    Audioguru FM Tx

    Hi guru hehehehe I'm sure u have never made an electret mic. somewhere i read that his mic is very sensitive and can pick up all voices inside the room, like u said about your FM Tx. others said that you must talk near it.... from that, one deduce that it is posible to increase or decrease mic...
  19. walid1

    Audioguru FM Tx

    Hi guru thank you for your efforts to explain First, you skip my last questions with a colored table. with 1k the total = 762 ohm as u said with 10k the total = 2424 ohm, big difference I calculate Zin at the base the Ic=0.1 mA, Zin = 52K to make it 30K, Ic must = 0.2 mA If i do so, what are...
  20. walid1

    Audioguru FM Tx

    please don't skip the above questions, i forgot to ask this important one: what the optimum impedance value that mic like to connect with, that is R1// Zin of the next stage? thank u again
Top