1. MrsssSu

    Produce an oscillating Dc wave

    Hi People :), The reason why I will be needing an oscillating dc waveform is because I need it to be fed into the input of a comparator to produce high frequency square wave dc signal. I built this Wein Bridge Oscillator and it works fine to produce quite a high frequency sine wave. However, I...
  2. MrsssSu

    Produce high frequency square wave

    Hi readers:), When decreasing R1 value, output frequency will increase. However, I get bad waveform when high frequency. How do I get a good square wave (100kHz) using this LM 741 chip that I bought? Simulation is attached below for your reference and modification to the answer :)
  3. MrsssSu

    Generate Complementary PWM with dead time.

    I have a similar question to click here. However, in my case i am using ne 555 for logic gate inverter :). I have generated the complementary PWM and it works totally fine. My question is how to add a dead time between the pulses. From click here, people suggests to use an RC network, how do I...
  4. MrsssSu

    Is this part a tiny step-up converter?

    Hi People :), This is a design I saw at here. Does this highlighted part a tiny step-up voltage converter after it has been stepped down by the transformer in order to prevent voltage drop when a heavy load is connected? Thank you
  5. MrsssSu

    High current Step-down converter efficiency problem

    Hi People:), I am trying to build a synchronous step-down converter but my LT spice simulation shows poor efficiency. The picture above is at Here . I have attached my LT spice below for reference. May I know if this is the right way or anyone can correct my LT spice file and send it in the...
  6. MrsssSu

    Lithium ion charged at 5V 2A, why internal resistance is not 2.5 Ohms?

    Lithium ion cell are charged at 5V and 2A max. Following Ohm's Law, 5V/2A would mean at least a 2.5 Ohm internal resistance of battery. However, Lithium ion internal resistance is only about 0.28 Ohms. How is that possible :)?
  7. K

    Linear voltage converter (kinda)

    Good evening, I’m not an expert in electronic design by any means so please excuse any lack of understanding. I’m working on a current project where I need basically a linear voltage “adapter” I have an analog voltage DC signal of -10v to 10v and I need to somehow convert that to be between...
  8. MrsssSu

    Why my Relay short-circuited ?

    I have a relay but rated at 3A, 30V DC only similar to this. When I connect the Pole and NC directly using a lithium ion battery (4V), a fire occur and it shortcicruicted. However, when i measure the resistance betwwen 2 pins (Pole and NC), it reads 16 Ohms. What should i do :) ? Thank you for...
  9. MrsssSu

    Can I use 5V 30 Amps PSU on a Lithium ion battery charger module?

    Hi, if I use a 5V 30Amps Power Supply Unit to plug into the input of this Lithium ion battery charger module, is it fine since it will draw a limited output of 1A to charge the battery which it requires right ?
  10. MrsssSu

    Battery Charging Circuit efficiency

    Hi readers:), Click here . This link refers to making a lithium-ion battery charger using a BC 547. Question: How efficient is this circuit in (%) that is useful output power/ input power to charge a battery? I am planning to build a 4.2V charger but with a much higher ampere limit by...
  11. MrsssSu

    High Voltage PMOS recommendation

    Hi readers, is there a P-channel Mosfet with Vds of -400V but has very low Rds(On) because I want an efficient mosfet ? I a planning to power a 400V device and its negative terminal must be connected to ground (That's the reason why i use PMOS and not NMOS). I find a lot of NMOS that can...
  12. MrsssSu

    Will voltage across transformer drop when charge a lithium ion battery?

    If I have a 4W transformer that has high inductance, thick windings, (4V ,1 A) and converted to DC via a rectifier, in order to charge a lithium ion battery (low internal resistance) , will the output will still be slightly less than 4V or will it be very low (close to 0 which makes it...
  13. MrsssSu

    Maintain constant voltage across a variable load (op-amp)

    Hi readers :), Vin is fed with the PWM signal coming from an op-amp to be amplified and fed into the load R1 (1 Ohms). The purpose I design this is I want the voltage source to be a constant 5V which is independent of the load (1 Ohms or 100 Ohms). So basically, this circuit has an op-amp which...
  14. MrsssSu

    How to use PMOS mosfet?

    Hi readers, is this the correct way to power a PMOS mosfet? I am unfamiliar with PMOS but quite familiar with NMOS. Question: How to use PMOS to power a 10 Ohm Load? Thank you I attached LT Spice files below. Help me understand by attaching or posting a new schematic :) Thank you and have a nice...
  15. MrsssSu

    Regulate voltage using op amp

    Hi readers, I am doing an Op Amp voltage regulation of voltage drop across load. As you can see from diagram, I have a fluctuating_Vin (0V to 50V) and I want the voltage drop at load (100 Ohms) to be the same (14V) at all times no matter whether input voltage is 20V or 30V or 50V? Note: I...
  16. MrsssSu

    Convert triangle wave to sine wave.

    Hi readers, the IN node has triangular wave converted from square wave pulse. This Op-Amp acts as integrator. However, when I attach the same integrator circuit to convert this triangular wave (IN) to sine wave, the Output (OUT) I got is still quite triangular and not quite a good sine wave...
  17. Swaysceptile

    How do I calculate the voltage across a diode?

    How do I calculate the voltage across a diode using ideal, practical, and complete models? What are the steps? I can't find any good tutorials/resources on the internet. I know the formula, but kinda confused with those many resistors. Hope someone could help
  18. MrsssSu

    Amplify Flip Flop signal from NE 555 timer using transistors

    Above is the graph across R7 (Load). Hi readers, Flip Flop with Ne555 timer means turning on an led and another one off, as shown in picture, and this alternate on and off pattern continues. This video can be found at Click Here . I have succeeded in amplifying one of the 2 signal as shown in...
  19. MrsssSu

    PNP transistor to amplify square wave signal received at its base

    Above is the load power Hi People, I created this npn transistor circuit and it works fine. So basically, it receives this square wave impulse (0 to 2V) and send it to the 10 Ohm(Load) to be amplified to become (0 to 10V). Question: How to simulate the same way (Load Power Output should be...
  20. MrsssSu

    Current direction using transistors

    Hi readers, I am trying to simulate current flow in both direction of the load by using 4 relays or transistors. For example, in this circuit, the load will have left current flow when 2 of the switch or transistors are on and 2 of the switch are off. The opposite way applies too if 2 of the...
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