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  1. mrinalmani

    metal resistor's temperature coeffcient(TC) spread

    Hi! For reference purpose can you please tell us what was the divergence in the measured value of poly TC across batches. Also, what was the divergence in the absolute resistance value across batches. Thank you
  2. mrinalmani

    Push-pull output switches OFF momentarily after switching ON

    Unfortunately this is a simulation. And the turn-off is probably not due to stray inductance because adding nearly 5nH inductance in series with the speed up capacitor does not change the result. However adding a 100 Ohm resistor in series with the BJT output and totem pole input eliminates...
  3. mrinalmani

    Push-pull output switches OFF momentarily after switching ON

    Hi A 3.3V PWM input is stepped up to 12V using a BJT. The BJT has a speed up capacitor of 50pF. The output from the BJT is fed to an inverted push-pull stage. (Inverted as in the P MOSFET is at the bottom and N at the top) The problem is that soon after the BJT switches ON, it immediately...
  4. mrinalmani

    [SOLVED] Faster PMOS turn-off time

    I see from the datasheet of your P-MOS that the reverse recovery time of the body diode is very large, 400ns! This explains why it takes a long time for the output to fall down in absence of a resistive load. Changing the P-MOS with a faster recovery diode should enhance the time further. 360...
  5. mrinalmani

    Differential mode amplifier with one input tied to ground.

    I appears to me that the circuit would make sense if the sensor's local ground bounced higher than the op-amp's local ground ie. VEE But if the sensor ground goes below the op-amp ground, things could be bad.
  6. mrinalmani

    Differential mode amplifier with one input tied to ground.

    I have a current sense resistor whose one terminal is ground itself. But the resistor is in a noisy area so I have used differential routing. I was wondering whether differential mode amplification will be of any good for suppressing noise and ground bounce. Please note that one of the input of...
  7. mrinalmani

    BJT: Are PNP transistors really indispensible when we can't do so much with NPNs?

    Everything that can be done with a PNP can also be done with an NPN. However in some cases, a PNP configuration may simplify the complexity arising from referencing signals to ground.
  8. mrinalmani

    will inverting op-amp work with no R1?

    Without the input resistor R1, the OP AMP will not work as an amplifier. It will work as a square wave generator with frequency equal to the the frequency of the input signal. However if the impedance of the input signal is comparable to the feedback impedance, the circuit may become unstable...
  9. mrinalmani

    Analog switch vs MOSFET

    Thanks for the reply! The capacitor must charge to around 2V in 2 to 3 micro-seconds. The voltage input can be approximated by a unit-step jump from 0 to 1V and then a 1st order ramp to 2V in 3us. The voltage accuracy must be around 1%, which means 10 to 20mV error is ok. To suppress overshoot...
  10. mrinalmani

    Analog switch vs MOSFET

    Hello! I need to charge a 1nF capacitor upto a reference voltage of around 1 to 2 volts. A MOSFET doesn't serve the purpose because of the threshold issue. Can an analog switch solve the problem? The capacitor must charge right upto the reference voltage without any drop due to threshold or...
  11. mrinalmani

    Need help with voltage to current circuit!!!

    R1 provides thermal stability to the BJT. It helps to reduce the leakage current due to minority carriers at elevated temperatures. Although it can be removed, its good to use it.
  12. mrinalmani

    Help me to understand relay datasheet

    No, that's not how you should interpret it! A normal reaction force of 1G acts when an object is lying stationary on a surface. When the object is falling freely, it does not experience any force. (Just like in space) However, at the instant when a falling object hits the ground it experiences a...
  13. mrinalmani

    Peak detector temperature compensation

    Well, since op-amp based precision rectifiers are out of option due to saturation delay. You may have to add a good amount of extra circuitry to accomplish the same task without using precision rectifiers. Consider the following alternative: 1. Replace the capacitor C1 with a resistor. Connect...
  14. mrinalmani

    Noise from FET controlled by comparator

    There we have.... "inductor switching at 100KHZ!" 1. The switching of inductor is likely causing the comparator to swing. Note that when you switch-off the inductor, the ground pin of amp number 1 is floating and has possibility of acquiring a small voltage. 2. The swinging of comparator in turn...
  15. mrinalmani

    OPAMP output is high even if the two inputs are low

    Well well well.... instead of editing, I seem to have deleted a post. But anyway... Another +1... thanks!
  16. mrinalmani

    Noise from FET controlled by comparator

    The reason may be coupling of leakage magnetic field from to coil with the traces of the PCB and thereby inducing voltage at the ADC input. Is the coil close to the ADC? Another reason may be ringing of the rail voltage due to the coil and some adventitious parasitic capacitance. Place a 10 ohm...
  17. mrinalmani

    [SOLVED] Oscilloscope parameters

    Now I get it... Thanks a lot!
  18. mrinalmani

    [SOLVED] Oscilloscope parameters

    Ok, I got it somewhat. But is the plot obtained by equivalent sampling an accurate picture of what is going on? Consider the following.... Suppose the "actual" sampling interval is 100ns. Now if there is a local oscillation or spike that lasts less than, say 30ns. Then will the scope show this...
  19. mrinalmani

    [SOLVED] Oscilloscope parameters

    I still quite don't understand "equivalent" sampling rate (which by looking into specification sheets ,seems like a warehouse if the "actual" sampling rate were a retail outlet!!)
  20. mrinalmani

    [SOLVED] Ground shifting from one level to another

    Ok, I finally wanna ask... is the use of opto-couplers an industry standard practice? Someone with experience, please provide feedback...

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