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Type: Posts; User: crutschow

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  1. Closed: Re: Sampling Bandwidth vs. Bandwidth in Tracking Mode of a Sample/Track and Hold

    Sampling bandwidth is defined by the Nyquist criteria, i.e. the sampling frequency must be greater than twice the highest signal frequency of interest to reconstruct the waveform (in practice a...
  2. Closed: Re: Full wave bridge rectifier but doing half wave

    Unless you got an autotransformer, the primary and secondary of a transformer are isolated.

    And I don't see how AC main's grounds can be "isolated".
    By definition all AC grounds go to earth.
  3. Closed: Re: Full wave bridge rectifier but doing half wave

    Yes.
    And adjust both inputs to have identical gain.
    You can check that by connecting both inputs to the same signal (such as the AC voltage) and adjusting for the minimum displayed voltage.
  4. Closed: Re: Full wave bridge rectifier but doing half wave

    Yes, it's a common mistake for newbies to connect the input and output of a bridge circuit to a common ground, which will not work.
    It you look at the current path, you will see why.
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    Closed: Re: how does a coaxial cable work?

    The forward signal current is carried by the inner conductor and the return signal current by the outer conductor, but the outer conductor us typically maintained at ground potential at both ends of...
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    Closed: Re: impedance of antenna

    The impedance of the antenna (ignoring any parasitic losses) is its radiation resistance to free space, and is determined by the physical/geometric design of the antenna and the frequency.
    Some...
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    Closed: Re: Overvoltage Protection

    You have no DC supply connection to the transistor emitter, so it won't work.
  8. [SOLVED]Closed: Re: Ultra low-power timer to make a power saving circuit

    Here's a reference for a CD4060 circuit that will give up to a 24-hour delay.
    If you omit the transistor, LEDs, and relay, the average current draw should be only a few microamps.
    That could likely...
  9. [SOLVED]Closed: Re: solution to over current / protection circuit

    How about adding an invert gate to the motor board powered by the motor power.
    The inhibit signal is then low, so a power loss from the ucontroller will turn off the motor board (adding a pull-down...
  10. Closed: Re: Power Supply Design for timer application

    Delete the 7805 and use the common 5V wallwort.
    They are cheap and provide isolation from the mains.
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    Closed: Re: How to find Vec of an active mode pnp

    It that's a simulation, just run a transient simulation and plot the voltage at that node.
  12. Closed: Re: Accurate mains zero cross detector circuit without optocoupler

    Why do you call that a "wear-out" component?
    Provided they are used well within their ratings, opto-couplers are just as reliable and long-lasting as most other solid-state devices.
  13. Closed: Re: Ramping a reference voltage up from, or down to zero volts, over ~200us

    Below is the simulation of a example circuit using 4 resistors in a binary ladder network to give the 16 steps.
    It is shown connected to the 5V outputs of a binary counter (outputs 1, 2, 3, and 4),...
  14. Closed: Re: Ramping a reference voltage up from, or down to zero volts, over ~200us

    Can you use a microcontroller with a DAC output (not PWM)?
    Or use an external DAC?
    Or, if you have four spare digital outputs on the micro, you could use a simple 4-resistor ladder network with an...
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    Closed: Re: Discrete transistor voltage regulator

    Just use a LM317 regulator with one 120 ohm resistor and one 500 ohm pot (plus a couple decoupling caps).
    That will allow adjustment of the output from 1.25V (the stable internal reference voltage)...
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    Closed: Re: Discrete transistor voltage regulator

    Is that AC or DC?

    Making a simple discrete regulator whose output can go below its reference voltage is problematic, unless you use an op amp.
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    Closed: Re: Discrete transistor voltage regulator

    That circuit uses the base-emitter voltage of Q1 and the forward diode drop of D1 as a voltage reference, so the minimum output voltage would be about 1.3V.
    If you eliminated D1 and connected the...
  18. Closed: Re: Recommend a pulse filter? If pulse longer than 100ms, output, otherwise not

    The simplest is just to use an RC delay with a Schmitt-trigger input, such as a CD40106, and tweak the value of the resistor to get the desired value, if needed.
    LTspice simulation below:
    There is...
  19. Closed: Re: Recommend a pulse filter? If pulse longer than 100ms, output, otherwise not

    Do you have a digital clock signal available?
  20. Closed: Re: Analog realization of trignometric function

    Here's a way to approximate the sine function using an analog multiplier (from this paper.).

    156906
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    [SOLVED]Closed: Re: Average vs RMS load-current for LDO design

    A significant point missed is that RMS current only works as an indication of power with a resistive load.
    For a constant voltage load, such as a switching power supply, the average current is the...
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    [SOLVED]Closed: Re: Average vs RMS load-current for LDO design

    As I stated, for a steady DC output, such as from a linear regulator, the average current is the same as the RMS current (for DC the RMS calculation is trivial).
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    [SOLVED]Closed: Re: Average vs RMS load-current for LDO design

    For a DC current, the average and the RMS are the same.
  24. Closed: Re: Determining output impedance in LT SPICE

    Well, commonly when the term transistor is used without any further information, BJTs are being referred to.
    So you'll have to pardon me If I didn't realize you were referring to MOSFETs.
  25. Closed: Re: Determining output impedance in LT SPICE

    For gm, you can vary Ib and do waveform arithmetic of Ic/Vbe (right-click on the waveform title).

    For output impedance, you can vary the collector voltage and do waveform arithmetic of Vce/Ic for...
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