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  1. audioguru2

    Current monitor/sensor

    Your circuits with an opamp plus common-emitter transistors have too much voltage gain so they will probably oscillate. I showed two circuits with emitter-follower driver and output transistors that will not oscillate. But if you use PNP transistors the output voltage will not be able to go near...
  2. audioguru2

    Current monitor/sensor

    Your amplifier will oscillate because its transistors provide voltage gain. Then at a frequency where the opamp's phase shift would cause oscillation, its gain is less than 1 so it does not oscillate, but the total gain with the transistors is higher than 1 so the entire amplifier will oscillate...
  3. audioguru2

    Current monitor/sensor

    If you connect two transistors in parallel then each needs an emitter resistor so that they share the current fairly equally. The opamp will probably not have enough output current to drive output transistors without adding a driver transistor. I sketched a circuit with a PNP driver transistor...
  4. audioguru2

    Capacitor charging using low voltage supply

    The heating of a zener diode wastes power. It is simply the voltage across it times the current in it to give the number of Watts of heating.
  5. audioguru2

    question about PIR

    If it is then shorting D to S will keep it always turned on, but not cause the circuit to think there is always motion which needs an AC signal created by the Fresnel lens. The circuit will simply do whatever it does when the FIR is exposed to continuous IR light. I am surprised to see that it...
  6. audioguru2

    question about PIR

    You could measure the one you have to find the positive supply pin, the 0V ground pin and the output pin. Then if you short the output it might become destroyed.
  7. audioguru2

    2:1 stereo mixer/ ch1 mutes channel 2Hello

    An IC is designed and produced when there is enough demand for it so the manufacturer can make some profit from it. You might be the only person who needs an IC to do what you want so I doubt if there is one or that there will ever be one. You or somebody could design a circuit to do it.
  8. audioguru2

    question about PIR

    Whatever you have does not look like a PIR motion detector because it does not have a Fresnel lens. It is anybody's guess what its 3 pins are for. It doesn't even have a manufacturer's logo or a part number printed on it for you to look at its datasheet.
  9. audioguru2

    question about PIR

    A PIR probably does not have Mosfet pins. Most have an ordinary little transistor at the output that drives an external relay, power transistor or power Mosfet. If you put a jumper across its two output pins then it will probably stay turned on.
  10. audioguru2

    0-30 Vdc Stabilized Power Supply

    The TIP41 has an fT of only 3MHz so it is slow and its delays will probably cause the output amplifier to oscillate and have transient problems. The BD139 that should be used is very fast with an fT of 190MHz. The hFE is not important because the minimum hFE of one of the two 2N3055 output...
  11. audioguru2

    Current monitor/sensor

    Your circuit is missing a resistor from the collector of T2 to the base of the PNP output transistor to limit the base current. T2 will probably overheat without it. The PNP output transistor is missing a resistor from its base to its emitter to help turn it off. Both transistors add delay and...
  12. audioguru2

    RF - separate transmitter and transceiver antennas for half duplex

    Why use two antennas when only one is used at a time? My FRS radios operate in half-duplex and their frequency is so high that the single antenna is tiny. Only a single antenna is needed.
  13. audioguru2

    the finer points of electronics - I

    Flippityflop, I do not know what you are talking about. You show two opdinary diodes, not zener (avalanche) diodes. Why does your circuit have two zener diodes? There is no such thing as "an ambient voltage". Your circuit has no input, no output, no power supply, no biasing for the active...
  14. audioguru2

    the finer points of electronics - I

    If all you can think about is push and pull then look at the push-pull output of an amplifier where one transistor pulls the output positive and another transistor pushes the output negative.
  15. audioguru2

    the finer points of electronics - I

    The battery and the capacitor are simply connected in parallel. There is no ground, no push and no pull.
  16. audioguru2

    the finer points of electronics - I

    The "ground" of a circuit is simply just a common voltage that is usually 0V and is also part of the input and output wires. Sometimes the "ground" of a circuit is connected to earth ground.
  17. audioguru2

    can an ammeter damage zeners??

    An Ammeter uses a resistor in series with the load and displays the voltage dropped across the resistor using Ohm's Law to do the scaling. If the voltage is low in the circuit you are measuring the current in, then the reading is much too low.
  18. audioguru2

    Light data transmissions

    Like you were told on the other website forum, it is impossible.
  19. audioguru2

    Simple voltage regulator

    You make no sense because your circuit has no input resistor. Its input is the (+) input of the opamp.
  20. audioguru2

    0-30V 3A - I need some answers

    The original circuit has errors. So we fixed it in the forum. A maximum voltage from P2 is 1.7V when R18 is WRONG at 56k. When we fixed the original circuit we changed R18 to 33k and added a 100k calibration trimpot in series so when the trimpot is about 46.7k then the total with 33k is 79.7k...
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