Circuits & Schematics: frequency meter - 3

21. Use current-mirror biasing to avoid squegging in RF oscillators
    Madhu Siddalingaiah
    Circuits Oscillators Texas Instruments LM3046
    .. Sometimes called motor boating, squegging causes oscillators to start and stop at frequencies much lower than the frequency of interest. Viewed on an oscilloscope, squegging looks like bursts of oscillations. On a spectrum ...
    Mar 11, 2025

22. A simple, purely analog -130 dB THD sine wave generator
    Christopher Paul
    Circuits Oscillators onsemi NE570 SA571
    .. it’s worth recalling certain requirements for an analog oscillator: a feedback circuit which, at the oscillation frequency F OSC Hz, has a loop gain magnitude of unity and a phase shift of either 0 or a multiple of 360 ...
    Mar 7, 2025

23. Simple setup tests bit-error rate
    Israel Schneiderman
    Circuits Digital Texas Instruments LM393 SN74HC74 SN74HC86
    .. implementing a 1-bit delay detects the error. You can display error pulses on an oscilloscope or count them by using a frequency counter. Figure 2 shows a typical test setup. You modulate the RF generator at the prescribed data ...
    Mar 4, 2025
24. 1 A, 20V PWM DAC current source with tracking preregulator
    Stephen Woodward
    Circuits Supply Microchip MIC2253
    .. Q2’s IC control current generation. The daisy chain of three 1N4001 diodes provides bias for Q2 and Q4. The PWM input frequency is assumed to be 10 kHz or thereabouts. Ripple filtering is the purpose of C1 and C2 and gets some help ...
    Mar 4, 2025
25. 1-A, 20-V, PWM-controlled current source
    Stephen Woodward
    Circuits Supply ON Semiconductor LM337
    .. analog subtraction” ( Ref. 1 ). Since ripple filter C1 and C2 capacitors are shown sized for 8 bits and a 10-kHz PWM frequency, for this scheme to work properly with different frequency and resolution, the capacitances will need ...
    Feb 7, 2025
26. Metal detector uses single IC
    Rachel Hageman Steve Hageman
    Circuits Measurement National Semiconductor LM389
    .. circuit in Figure 1 was to locate coins, but it applies wherever you need to locate metal objects. The circuit uses a beat-frequency technique: Whenever a metal object comes close to the search coil, the metal causes the coil’s ...
    .. because they will lock with each other, thereby reducing the search oscillator’s sensitivity. You can add a meter output for visual or automatic control by adding a highpass filter to the LM389’s output. This highpass ...
    Feb 5, 2025
27. How to collect free energy from atmosphere
    Swagatam Majumdar
    Circuits Bad Prescriptions Supply
    .. free energy collector circuit helps to convert surrounding radio frequency waves to electric power and can provide 40 watts to 10 watts indefinitely. The circuit concept An ...
    Jan 15, 2025
28. Capture 16-bit readings of 8 thermistors in less than 1 second for $2
    Stephen Woodward
    Circuits Measurement Signal Processing, Filters Texas Instruments CD74HC4051 CD74HC4053
    .. Shortly thereafter the idea morphed into an uncomplicated, inexpensive, and fairly fast (1 MHz), low power voltage to frequency converter (VFC) “Voltage inverter design idea transmogrifies into a 1 MHz VFC” ( Ref. 2 ). ...
    Jan 14, 2025
29. An ultra low distortion oscillator with THD below -140 dB
    Vojtech Janásek
    Circuits Oscillators Measurement National Semiconductor LME49710
    .. for measuring parameters such as harmonic distortion or effective number of bits. A notch filter removes the fundamental frequency from the oscillators signal for testing harmonic distortion. A low-distortion oscillator is necessary ...
    Jan 10, 2025
30. Sweep generator with marker
    Cor van Rij
    Circuits Oscillators Measurement Diodes NE555
    .. FET Q1 and is disabled. The charging of the 330 nF is paused for a short time. This creates a brigther image at the marker frequency. Materials on the topic Datasheet Texas Instruments LM324 Datasheet Diodes NE555 Datasheet ON ...
    Jan 7, 2025

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