1. MrsssSu

    Small pull-down resistor for mosfet (fast switching, high capacitance)

    Hi readers, When I used this IRF 3205 which has high capacitance between the Gate-Source of the mosfet, whenever I add a lower pull-down resistor, the switching becomes faster and faster (visible nice square wave). For my case, for IRF 3205 to fast switching at 20kHz (nice square wave), it would...
  2. MrsssSu

    PS2501 optocoupler LT Spice Library File

    Hi, is there anyone having this PS 2501 optocoupler library from LT Spice. Pardon Me, I couldn't find on the internet :). Please attach it below. Thank you
  3. A

    Finding the gain expression for this CMOS operational transconductance amplifier

    So here's the circuit: I think M2 is a common source amplifier and M4 a common gate amplifier, so they form a cascode amplifier where the gain is given by : Av = -gm2 * r0, r0 is the impedance at the node where the drain of the common gate amplifier is at (Vop). r0 = ( [rds8 // (rds2a * (...
  4. MrsssSu

    PNP and NPN recommendation for mosfet driver

    Dear readers, Above is taken from here . Can anyone recommend transistor Q1 (npn) and Q2 (pnp) to me for driving a mosfet at a 100kHz or higher. What are some of the common best fast switching Q1 and Q2 that can handle high current and high frequency PWM at its base ? Thank you :)
  5. MrsssSu

    Optocoupler for high frequency

    Dear Readers, I got this PS2501 optocoupler datasheet at here. In the image shown, the rise time and fall time is microseconds and I am afraid it's not suited for my needs as it will produce some switching losses in H-bridge circuit running at 100kHz minimum. Are there any very-high speed...
  6. MrsssSu

    NE 555 (On , Off, ON) when subjected to different input voltage

    Hi readers, :) I found this at Click here This is an example of a disconnect and reconnect circuit using NE555. This means that the state of load will be (High, then, Low, them High). However, when I simulated using LT Spice it just give me (Low and High only). Does anyone know how to make the...
  7. 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...
  8. 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 :)
  9. 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...
  10. 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
  11. 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...
  12. MrsssSu

    Buck Converter (Wide range of Input Voltage to Output a fixed Voltage)

    Hi People :), This is a step up dc to dc converter. This schematic inputs a 15V and outputs a 22V DC. However, I want the input range to be between 3V to 50V and all gives the same constant 22V DC output current. How can this be done with UC 3845. I have attached the schematics below and spice...
  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

    Charging circuit modifications

    Hi. above is a charging cut-off circuit. As you can see in my demo. when voltage source is 5V, the load (R9) has 5W power. When voltage drops to 4V, the load (R9) has 0 W (cut off). However, my lithium ion charging pin for my battery is 4.26V. Thus, when battery fully charged at 4.2V, the...
  16. Selvedin

    How to make a flashing switch from a Transistor

    Hello guys, I need to make a circuit in which a transistor acts like a flashing switch. I watched some videos but the Problem is that I don't have the exact same components as in the Video shown and so my project fails. Can you help me? Kind regards to all good people