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Recent content by strahd_von_zarovich

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    Bipolar Current Source(Improved Howland Current Source)

    Hi everyone, I am trying to understand the constant current source at figure below. I couldn't understand the purpose of R6. The circuit just works as fine without R6. What is the purpose of R6? Thanks in advance.
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    Optic Power Meter Repair

    Hi everyone, I am trying to repair my optic power meter. However, I couldn't find the exact IC which is damaged. I am %95 sure :LOL: It is a TIA. I coulnd't find it's feedback resistor, so probably the gain resistor is inside the chip. Also, there are digital switching ICs on the board, so I...
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    Differential Amplifier Calculations

    Hi Everyone, I am trying to understand what did I do wrong. When I set all the capacitors the same value and impedance of R2||C5 to R1 , the output should be V2-V1 and if they are also equal then the output should be zero. However, in LTSpice, I cant get the same result.
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    [SOLVED] Amplifier Board Repair

    Dear Tony, thank you very much for your help, it really looks like that :) . It's NXP's NPN/PNP transistor model which is PBSS4160DPN.
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    [SOLVED] Amplifier Board Repair

    Dear Tony, I desoldered the component, they are short circuit on the board. Pin-5 and Pin-2 are connected to the another opamp's output. And either Pin-1 or Pin-4 is output. I think with these connections it is less likely an opamp.
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    [SOLVED] Amplifier Board Repair

    Hi everyone, While I was testing an amplifier board, I accidently short circuited the output and damaged the IC below. I searched for it's device marking on the internet but I coulnd't find it. Here is some information if it gives any clue: Pin-1 and Pin-4 are short circuit on the board...
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    How to convert ADC data to dBm

    Hi Everyone, I collect data from ADCs on my board. I couldn't figure out how to convert them to dBm on frequency spectrum. I wrote a Matlab code but it doesn't give me the correct results. Sampling Rate : 250MS , ADC Resolution: 16bit, Input Impedance: 50ohm FsChan = 250e6; % sampling...
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    Xilinx FPGA with Erased QR Code

    Hi everyone, I have bought ten Kintex-7 FPGA from China which their QR codes are erased and I tested them on my boards. I was expecting problems since I thought they are fake parts, but they are working without a problem. Even 10Gbit GTX pins are seems to work perfectly without an issue. They...
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    What are these structures in RF Amplifier

    Hi everyone, I am trying to understand the structures in an RF amplifier. I am not familier with production processes. What are these structures which I marked them in the picture below? I thought they are resistance but there are wirebonds on them. What is the blackish material, is it...
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    RF Transistor Model and Company Name

    Hi everyone, I am trying to find the the transistor(Phemt) below to repair my rf amplifier. The logo looks very familier but I coulnd't find the company. Can you tell me the company name, so I can search it at least in their websites. :) Thanks in advance.
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    Which ICs are Appropriate for Generating Very High Speed Pulse Waveforms

    Hi Klaus, Most probably I will design an amplifier stage for voltage and current requirements. At this stage, I just need to find the correct way, so I can deep dive into the design. If I use something like a high speed DAC, the controller will be an FPGA. If I there is some kind of...
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    Which ICs are Appropriate for Generating Very High Speed Pulse Waveforms

    Hi Dana, thank you very much for your answer. Delays between channels, and amplitude of signals must be changeable, so that's why I am actually looking for an IC. Probably pure analog solution will be very hard. :)
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    Which ICs are Appropriate for Generating Very High Speed Pulse Waveforms

    Hi everyone, I need to design high speed pulse waveform generator. Minimum pulse width must be lower than 300ps and rise-fall time must be lower than 100ps. Delay resolution must be lower than 100ps between channels. What is the best way to do it. I worked on high speed DACs with JESD204B...
  14. S

    How to Test Ram Speed With Kintex-7

    Hi Everyone, I've designed a FPGA board. There are 4 DDR3L RAM ICs on the board and I want to test RAM communication speed. What is the proper way to do it? Thanks in advance.
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    Xilinx Kintex-7 FPGA Temperature Problem

    Hi Everyone, I found the problem when I was testing the second board. Fortunately, I couldn't program the second board at all. Then I realized that the IC which is connected to the reset circuitry didn't provide right output. Turns out, I did a mistake on the logic level. While the IC was...
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