Circuits & Schematics: frequency meter - 9

81. Simple log-scale audio meter
    Nick Cornford
    Circuits Audio Measurement Texas Instruments TL081
    .. diode-drops’-worth in the process. (No, the V F s don’t match exactly, except momentarily, but no matter.) The meter now shows the log of negative-input half-cycle peaks, the needle falling back as the capacitor discharges ...
    Jan 22, 2024

82. Gated 555 astable hits the ground running
    Stephen Woodward
    Circuits Oscillators Texas Instruments LMC555 SN74HC04
    .. classic and versatile 555 finds its way into many low to moderate frequency oscillator applications. Some of these require the ability to selectively gate oscillation on and off ...
    Jan 18, 2024

83. A simple, accurate, and efficient charge pump voltage inverter for $1 (in singles)
    Stephen Woodward
    Circuits Supply Texas Instruments CD4053B
    .. a cycle that begins with C2 being charged to V IN via U1a, then completes by partially discharging C2 into C3 via U1b. Pump frequency is roughly 100 kHz under control of the U1c Schmidt trigger style oscillator, so that a charge transfer ...
    Jan 10, 2024
84. Squashed triangles: sines, but with teeth? Part 1
    Nick Cornford
    Circuits Oscillators Texas Instruments LM393 TL081 TLV237x
    .. is a square wave, with an exponential tri-wave present on C T . While the duty cycle is exactly 50% and the operating frequency is stable with supply variations assuming balanced power rails and a rail-to-rail op-amp output neither ...
    Jan 8, 2024
85. Adding one resistor improves anemometer analog linearity to better than ±0.5%
    Stephen Woodward
    Circuits Analogue Design Measurement Texas Instruments LM10 LMC555 2N5089
    .. trigger early by an amount proportional to anti-log Q2’s collector current. This shortens VFC period and raises VFC frequency by a nonlinearity-correcting factor and results in Figure 6. Figure 6. Improved analog linearity ...
    Dec 29, 2023
86. Linear and switcher LED supplies combine, overcome disadvantages of each topology
    Fabien Franc
    Circuits Supply onsemi CAT4101 CAT4201
    .. especially when the supply voltage drops and approaches the LED forward voltage. In automotive applications, RFI (radio-frequency interference) is a major concern. EMI/RFI filters are recommended in front of the switching converters ...
    Dec 28, 2023
87. New full-wave precision rectifier has versatile current mode outputs
    Stephen Woodward
    Circuits Analogue Design Signal Processing, Filters Texas Instruments TLV2371
    .. quadrature signals are summed, the result is an approximate (roughly 3% nonlinearity) triangular waveshape at double the frequency of the sine, with amplitude proportional to the sine’s. Adjustment of the quasi-triangle’s ...
    Dec 22, 2023
88. Multivibrator also makes true-zero output of the op-amp
    Peter Demchenko
    Circuits Signal Processing, Filters Supply STMicroelectronics BAR43A
    .. applications. Dual Schottky BAR43A performs like a full-wave rectifier, its symmetry reduces the level of the multivibrator frequency in the output noise. The same can be said about the symmetry of the multivibrator itself. Like its ...
    Dec 19, 2023
89. Bridge measures small capacitance in presence of large strays
    Jeff Witt
    Circuits Measurement Analog Devices LT1004 LT1413 LT1462 LTC1043
    .. Two traditional circuit types have drawbacks: integrators are sensitive to noise at the comparator and voltage-to-frequency converters typically measure stray as well as sensor capacitance. The capacitance bridge presented here ...
    Dec 18, 2023
90. Single supply function generator outputs buffered squares, triangles, and sines
    Stephen Woodward
    Circuits Oscillators Texas Instruments TLV9064
    .. V DD /2) squares and triangles. The peak-to-peak amplitude of the latter is fixed by R5 and R6 at 0.909V DD , and the frequency of both is settable over two decades (and perhaps a bit more) by R1C1. Conversion of A2’s ...
    Dec 13, 2023

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