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Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.


  1. J

    Ultrasonic Cleaner 500 watt

    I am making an ultrasonic transducer cleaning circuit. Please guide me on how to make it as I am not an expert in electronics but have some skill in it. It has to be a few hundred watts in power, say 500 watts. Here is my idea: As a power source I am using a variac rated at 2000 watts. It is...
  2. M

    Grounding the base of an NPN BJt

    Hello, I made a simple circuit connecting an LED to the collector of an npn transistor. After I applied some 3V, I noticed the LED lit up and very dim of course. I simply grounded the base and the LED turned off. When I removed the ground, suddenly the LED turns nice and bright but not to the...
  3. A

    2SA1708 and 2SC4488 NPN Transistors for SPICE

    Hi there! I am currently looking for 2SA1708 and 2SC4488 transistor models to integrate into Spice, but I could not find any model on the web. Could you please help me if you have the related models? Or can you please give me feedback about what parameters are the most important ones to model...
  4. M

    Square wave using LM319 Comparator.

    Hi People, I am using an LM 319 High Speed Comparator to produce high frequency square wave as shown. However, from the first diagram, I assembled the connections based on second diagram, it does not work. The V+ and V- that is negative rail and positive rail I used is +9 and -9 V from 2...
  5. SeanYB

    C2073 Transistor is hot on standby and the channel is silent. Why?

    The power button of the device was broken and the fuse was burned. So, I changed the fuse, and then I directly connected it over the switch. It can be turned on and there is sound, but I accidentally found that there seems to be a channel that is silent. I changed the input terminal, but it...
  6. B

    Meaning of codes on two transistors.

    This is my first post. I have a Marantz PM-66SE KI. The left speaker and headphone outputs are almost completely silent. This might be due to dead transistors. I opened the unit and I noted the codes on the transistors screwed onto the heat sink. They are A1265N R 7K and C3182N R 8A I...
  7. N

    Microwave frequencies emitter circuit

    Hello, For my project I need to build a variable frequency emitter, with a frequency between 100MHz and 3500Mhz. I saw some simple RF circuits on the Internet but I don't think they can reach such high frequencies. Here is a circuit I've found : I don't need to transfer any information, so...
  8. B

    IR Circuit question

    I'm trying to make a simple IR circuit that energizes a coil when the detector "sees" the beam (refer to attached schematic). The problem is when the everything is active, I have almost no current at the coil. Why am I losing so much current? I suspect it's because the base of the NPN transistor...
  9. L

    Enable Pin vs Shutdown Pin

    Hello Everyone, I have a problem here... I am designing a board that I need a low voltage cutoff for... I want to use the Enable pin to do this... I have the circuit designed for a shutdown pin, but this is the opposite of the enable pin, right??? Here is my design in LTSpice... So here are...
  10. K

    Need help interpreting an old circuit diagram: Transistor and RF Transformer

    I will start by apologizing for asking what may be very simple questions; I am a scientist who has built some simple circuits before, but I am not by any means an expert in circuitry. I am trying to build a simple circuit based on a diagram in a modern laboratory textbook, but the textbook's...
  11. 1

    TO-247 bent pins

    Long-short question: I am working at a new project, a lab power supply. I used some TIP3055 for this project. Those TIP3055 were recovered from another project and the pins were a little bit short. I was forced to bend them from near the plastic case to make them fit to the new project PCB...
  12. F

    Resistor Parasitic Capacitance and RF Operating point

    As a reference to my question; I know that a 10K ohm resistor that has a parasitic capacitance of .3pF at 200MHz will have a actual impedance value of 2.564K ohms. If this resistor is used in a bias network for an RF amplifier, how does this shift in resistance effect the RF operating point...
  13. S

    Bipolar transistor

    Hello everyone, I have a little issue here. I know it's not really hard but it has been a moment since I've worked with circuits like this and transistors, so I can't figure out this circuit... The question is: In DC analysis, calculate the bipolar transistor's voltages Vb, Ve, Vc. Deduce the...
  14. sr13579

    How to make a simple oscillator with transistor and Capacitor?

    I provided a circuit which should discharge at a specific time. But this circuit is not working as an oscillator. How should I make circuit which will give me oscillation?
  15. mading2018

    Temperature with heatsinkcalculator software

    Hello :happy:, I have in the recent days tried to simulate the temperatures levels in a charger (AC/DC-module) in a Heatsinkcalculator software: **broken link removed** Based on the power losses calculations for half-bridge, where we have two MOSFETs that are operating one at the time, where...
  16. T

    Transistor tester won't start self test mode

    I've got a transistor tester 1.12k version and it says it's not calibrated. When I connect the 3 different pins together it asks if I want to run self test mode. I press the button within 2 seconds (as the manual suggests) but instead of calibration menu it just makes a single test and displays...
  17. sr13579

    How am I supposed to get a plot from this code on WeSpice(NGspice) engine?

    There is the code ’npn transistor vbias 3 0 dc 5v vs 1 0 dc 0v rb 1 2 20k rc 3 4 2k q 4 2 0 mynpn .model mynpn npn (BF=175 IS=1e-17 VA=75 BR=2) .dc vs 0 5 0.5 .plot dc v(3) -i(vbias) .end ’ But the output is showing a negative going down. How to get the graph of the plot with this app called...
  18. F

    About the function of transistor

    Here i attached a simple wireless power transmission circuit. What is the function of transistor here?
  19. Ginger FerrroChrome

    Newbie trying to replace a transistor (Pioneer 1203 31, Q409)

    Hello! 'Name's Forrest! Or Ginger, whatever you prefer. So, I'm pretty new at electronics repair, I've replaced a couple of laptop modules and put new belts on all of my cassette players, but I'm just now, for the first time, trying to soldier a component on a PCB (ironically I broke it trying...
  20. S

    Logic Buffers using discrete components

    Hello, If the digital output (LVCMOS 3V3) is heavily loaded , we may need to use buffer to meet Vih & Ioh (output high current) level of the receiver circuit. I prefer not use the stand-alone Buffer IC's . Can anyone guide me to design my own buffer circuit based on Transistors ?? Thanks Antony
  21. I

    Frequency Response Heterojunction Bipolar Transistor

    I have a project, first i need to find a circuit to Analyse/study the Frequency Response of Heterojunction Bipolar Transistor. Then simulate that circuit on SPICE (i'am using Orcad Cadence). Can someone help me finding a circuit as mentioned above???, I'm having difficulties finding one. Any...
  22. X

    Typical Application Connection IRAMX20UP60A

    Looking into the datasheet of the IRAMX20UP60A, I found a typical application connection which I am trying to understand. I attach a picture of the application circuit. The part inside the black square is what I don't understand. As far as I understand, if a low signal goes into the base of the...
  23. throbscottle

    NOS Transistor with brittle leads

    Happy Thursday everybody! I managed to get what is probably a genuine Toshiba 1996 2SA1302 with green epoxy, to repair a PA, and started bending it's leads to match the original which have a semi-circle bent into them, presumably to allow for thermal expansion. They creaked and crackled a bit...
  24. Y

    PNP Transistor - base voltage higher than collector

    Hi guys, Is it ok for the base voltage driving a PNP transistor to be higher than the collector voltage? I'm trying to throw the input to a HS088 doorbell board (see attached) high from a microcontroller in place of the button shown on the schematic - have been testing with Arduino UNO in this...
  25. E

    Class D amplifier for arduino

    I was playing about with transistor amplifiers nd I built this class D amplifier intended for use with the arduino ( or any other microcontroller) Thanks Matt!

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