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Type: Posts; User: crutschow

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  1. 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...
  2. [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...
  3. 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.
  5. 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.
  6. 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),...
  7. 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...
  11. 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...
  12. Closed: Re: Recommend a pulse filter? If pulse longer than 100ms, output, otherwise not

    Do you have a digital clock signal available?
  13. 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.
  17. 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.
  18. 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...
  19. [SOLVED]Closed: Re: type 1 compensation in voltage regulators

    As noted, the regulator feedback loop is DC.
  20. Closed: Re: sampling rate vs rate of change of input for control system

    No.
    You get 20 points with a 12-bit resolution for each point (sample).
    You are confusing time resolution with amplitude resolution.
  21. Closed: Re: sampling rate vs rate of change of input for control system

    That doesn't make sense.
    rps is a velocity, not a change in velocity.
    Do you mean 100rps/s change?
    How fast does the velocity change and what speed of correction you need?
    Also what are you...
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    Closed: Re: Digital De-emphais Error

    Sorry but there's way too little info to answer your question.
  23. Closed: Re: shunt 24V rail to reference voltage using opamp?

    An apparent problem is that the negative feedback loop has no compensation for the added loop gain from the transistor.
    That can lead to an unstable output.

    How is the 200mA bus current limit...
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    Closed: Re: Using AD627 with gain > 1000

    That's why gain is distributed over more than one stage since, with lower stage gain, the bandwidth of each stage can be higher.
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    Closed: Re: Using AD627 with gain > 1000

    Try it at the gain you want and see what happens.

    Alternately why not just add a rail-rail op amp gain stage at the output of the AD627?
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