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  1. audioguru2

    Ft of the transistor

    Yes because the transistor is a common base amplifier. There is no RF base signal, the base is shorted to ground at RF by C5.
  2. audioguru2

    Frequency response for a transistor amp.

    What is Xc=13000? Walid used the 0.1uF capacitor for European treble boost in his simulation. It is in parallel with the 470 ohm emitter resistor and its reactance equals 470 ohms at 3400Hz where the response is boosted +3dB.
  3. audioguru2

    12 V DC to a 220V AC Inverter AMplfier Design

    Yes they are fine. I made your huge schematic smaller and showed where lines cross over and do not join. Pin 7 of the CD4001 must be connected to ground. Your CD4047 and CD4001 didn't have +12V. The two capacitors are non-polarized metalized plastic (Oriental green caps). Your Mosfets are...
  4. audioguru2

    Electronic Stethoscope

    The first opamp amplifies the very low level from the microphone. The second opamp is an equal component Sallen and Key second-order Butterworth lowpass filter that should not have more gain than 1.6. A dual opamp is inexpensive because they are used in stereos. They are smaller than two...
  5. audioguru2

    building a generator

    My funace blower motor is powerful and I think it would make a good alternator. It is rated for 1200W. Electrical repair shops have rebuilt ones at good prices.
  6. audioguru2

    My 12 watt x2 stereo amplifier

    Hi Ben, I had some small 2-way speakers in cast aluminum boxes. I upgraded their 4 inch woofers for better 4 ohms ones. Then I added ports that were tuned to 75Hz. The boxes were a little small so I added some bass boost to the amplifiers. I made a clipping indicator circuit so I could see...
  7. audioguru2

    12 V DC to a 220V AC Inverter AMplfier Design

    Yeah. A 555 has a 200mA output current. An ordinary Cmos logic IC has only about 15mA with a 12V supply. A big difference. What do you think will happen to the two pairs of 2N3055 transistors that must share 50A when the inverter has a 500W load? Each transistor will conduct 25A. Their absolute...
  8. audioguru2

    dc to ac help

    If an ordinary 555 has a 15V supply, as an oscillator its output goes up to only about 13.8V and down almost to 0V. So the output is not 15VAC. A Cmos 555 like an LMC555, TLC555 or ICL7555 has an absolute max supply voltage of 15V and its output will swing up to exactly 15V and down to 0V if it...
  9. audioguru2

    12 V DC to a 220V AC Inverter AMplfier Design

    I just noticed an Edit that occured a while ago. Another argument about an ordinary low power Cmos oscillator. Texas Instruments says that the minimum resistor value should be 10k, not 1k. The capacitor has AC across it so it should be non-polarized. 1k with 4.7uF is wrong. 47k with 0.1uF is...
  10. audioguru2

    12 V DC to a 220V AC Inverter AMplfier Design

    Hi Kachew, I looked back at 6 pages and I couldn't find the final schematic for your modified sine-wave inverter.The last one had the Mosfets incorrectly connected as source followers. The CD4047 has a 100Hz clock output, a non-inverted 50Hz output and an inverted 50Hz output. When they are...
  11. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Kolonel, I agree that Q4 gets too hot in this project. When a 30VAC transformer is used so that the output can reach 30VDC at 3A then the Q4 gets much hotter. Then high voltage opamps must be used. Does your project exceed an output voltage of only 25VDC at 3A? Did you use the original...
  12. audioguru2

    Frequency response for a transistor amp.

    No Kevin. At the frequency where the reactance of the capacitor is equal to the resistor then the response is boosted exactly 3dB (times 1.414 in level). Just like in the curves from Walid.
  13. audioguru2

    Ft of the transistor

    No. C7 is in parallel with the 2pF of the transistor plus 5pF for stray wiring capacitance. The total of 11.7pF has a reactance the same as the emitter resistor at about 62MHz where the phase shift is 45 degrees. At 100MHz the phase shifrt is less, maybe 25 or 30 degrees. The base doesn't have...
  14. audioguru2

    Electronic Stethoscope 2

    Hi Soly, Your pcb is correct but you have the same size for a small 4.7uF electrolytic capacitor as for huge 470uF and 1000uF ones. The big ones will not fit. You show all metalized plastic capacitors as round (they are rectangular) and with only 0.1" between wires (they have 0.2" between...
  15. audioguru2

    Problem in an H-Bridge

    No, on-resistance is the resistance of the Mosfet in series with the motor. The motor's current through the resistance cause a voltage drop that is reduced from the voltage for the motor. The lower is the on-resistance then the lower is the voltage loss. The new Mosfet is more than 30 times...
  16. audioguru2

    Frequency response for a transistor amp.

    If they changed the corner frequency of pre-emphasis then all radios made up to then would sound wrong. It works good. They use compressors to reduce overload. Pre-emphasis and de-emphasis is done to reduce hiss. Then the signal to noise ratio is excellent. 2.1kHz is made with an RC of 75us. It...
  17. audioguru2

    help me read this circuit? please?

    An error on the schematic causes Q5 to be shorted.
  18. audioguru2

    Frequency response for a transistor amp.

    Hi Walid, FM radio stations and TV stations boost high audio frequencies like that. It is called "pre-emphasis". FM radios and TVs use a similar de-emphasis to cut the treble audio frequencies back down to normal and cut hiss at the same time. If a transmitter doesn't boost the treble audio...
  19. audioguru2

    Ft of the transistor

    I don't think class-C is ever used for audio. It would be far too distorted. Class-D amplifiers are very efficient because they are a switching device and their distortion is pretty low now. My FM transmitter has an oscillator with its collector output at the same phase as its emitter input. The...
  20. audioguru2

    How does one measure frequency response?

    Hi Quincy, Depending on how and how much your hearing has been overloaded, the frequency response of your hearing might be good or might be terrible. It is difficult to judge how much the levels are different between two frequencies. My hearing has always been pretty good because I avoided...
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