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Recent content by Johnny_YU

  1. J

    Puzzled by OPA and output noise

    Hi, Klaus Thank you for reply! I was on a business trip last week. I can't understand "3 side milling cut around the capacitor" in english, I know you want to tell me how to layout the PCB with the ceramic capacitors. Would you please show me some picture to let me...
  2. J

    Puzzled by OPA and output noise

    Hi, FvM Thank you for reply! I connected sensor positve input to the PCB-GND. But it doesn't be connected to the V+ of the first stage OPAMP. I'm sorry for the missing information of schematic. Please see picture 8, R19 is not connected. I used one board to do the test. I...
  3. J

    Puzzled by OPA and output noise

    Hi, Klaus Picture 1 is my PCB. Picture 2 is the first stage OPAMP circuit. Picture 3 shows that I use the scope probe to measure the output of the first OPAMP. Picture 4,5,6 shows the output of the first stage OPAMP, OPAMP is OPA379. Picture 7 shows the output of the first...
  4. J

    Puzzled by OPA and output noise

    Hi, all I use OPA376 and OPA344 to build a two stage high-pass non-inverting amplifier circuit, and a 4th low-pass filter. I made a two layers PCB. All the signals and Powers is on the top layer, the bottom layer is a ground plane. In this PCB Layout, the purple trace(20 mils) is...
  5. J

    Input and Output Voltage of OPA

    Hi, FvM Thank you for your reply! You are right. When I use a Multimeter(HIOKI DT4211), Vin+ is about 600mV. When I use a oscilloscope, Vin+ is about 220mV. - - - Updated - - - Hi, d123 Thank you for your reply! KlausST has answered your question. Here is my whole...
  6. J

    Input and Output Voltage of OPA

    Hi，All In my Schematic , 1.5V should be detected on the positive input of OPA, and the output voltage should be 1.5V. I use TINA to simulate the circuit , it shows the positive input of OPA is 1.494V,and the output voltage is 1.4948V. But, When I test this circuit , I found...
  7. J

    About To Make a Good Power system

    Hi, all in my circuit, there are: 1. one CC2541, a SOC for BLE. it runs with a 32M and a 32.768K crystal oscillator; 2. one EEPROM(400K speed); 3. one OPA379; 4. one NTC (Temperature Sensor) i use OPA to amplify the voltage signal associate with NTC, then use CC2541 to convert that voltage...
  8. J

    OPA quiescent current

    i get it, thank you!
  9. J

    OPA quiescent current

    if the supply voltage is 5V and quiescent current is 1uA, can i calculate the power dissipation in one minute use the formula "P = 5v * 1uA * 60sec "? is that correct? - - - Updated - - - if the supply voltage is 5V and quiescent current is 1uA, can i calculate the power dissipation in one...
  10. J

    OPA quiescent current

    Hi, all in all OPA Datasheet , i can find a parameter named "Quiescent Current per Amplifier", and its unit is uA. does this unit "uA" mean: uA per second or per minute , or others?
  11. J

    Capacitance load lead ringing or osillation

    Hi, dick_freebird Thank you for reply! I don't totally understand your reply about ground kick. i will seach for that , then i will back,thank you! - - - Updated - - - Hi, dick_freebird Thank you for reply! I don't totally understand your reply about ground kick. i will seach for that ...
  12. J

    Capacitance load lead ringing or osillation

    Hi,c_mitra Thank you for your reply! you mean ,i shuold think that like a RCL circuit? if i need to model it, i shuold choose a parallel RCL or a series RCL circuit? have you got any articles about explaining this situation?
  13. J

    Capacitance load lead ringing or osillation

    Hi, I find a lot of articles say: high capacitance loads can lead ringing or even severe osillation in power line. I don't understand. I think when drive a capacitance load , the load will draw more current from power supply. Because of the resistor of power supply, the supply voltage will...
  14. J

    first order low pass filter

    Hi,all I have a problem with the first order low pass filter. I kown how to calculate the H(s). H(s) = 1/(sRC+1), the bode diagram is below. In bode diagram , the slope is -20dB, how to calculate that slope? Thank you
  15. J

    Problem With AD9747(DAC)

    Hi all! i having problem with AD9747. In AD9747 DATASHEET , mentioned two parameter named "MAIN DAC OUPUT" and "AUXILIARY DAC OUTPUT".I dont kown how to explain/understand them and what they do in DAC? Thank you!
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