Circuits & Schematics: power supply - 3

21. Self-oscillating sawtooth generator spans 5 decades of frequencies
    Christopher Paul
    Circuits Oscillators Analog Devices ADA4891-1 LM4041 LT1720
    .. many ways of generating analog sawtooth waveforms with oscillating circuits. Here’s a method that employs a single supply voltage rail to produce a buffered signal whose frequency can be varied over a range from 10 Hz to 1 MHz ...
    Feb 16, 2026

22. Full circle current loops: 4 mA-20 mA to 0 mA-20 mA
    Stephen Woodward
    Circuits Analogue Design Measurement Interfaces Texas Instruments TLV431
    .. Q1 extends Z1’s 15 mA max current limit while also reducing thermal effects. The net result holds Z1’s maximum power dissipation to single-digit milliwatts. With 0.1% precision R1 and R2 and the 0.5% tolerance TLV431B , better ...
    .. of 20 mA Input max overhead voltage is 8 V, output overhead is 9 V. Worst case (resistor limited) fault current with 24 V supply = 80 mA. Readers may notice a capacitor labeled “C A ” in Figures 1 and 2. This is the ...
    Feb 13, 2026
23. Another silly simple precision 0-20mA to 4/20mA converter
    Ashutosh Sapre
    Circuits Analogue Design Measurement Interfaces ON Semiconductor LM337
    .. along with a few passive components, to translate an input 0-20 mA current source (say from a sensor with a separate power source that outputs a 0-20 mA signal current) into a 4-20 mA two-wire transmitter current loop (a standard 2 ...
    .. of varying pot contact resistance. A 3-V minimum operating voltage allows as much as 1000E of loop resistance with a 24-V supply, for the basic circuit. It is a given that one of the loops will (need to) be floating. This is usually the ...
    Feb 13, 2026
24. Transformerless 85-260VAC to 12VDC-0.2A power supply
    Hesam Moshiri
    Circuits Supply Diodes AL17150
    .. the AL17150 high-voltage step-down controller chip. Figure 1. Schematic diagram transformerless 85-260 VAC to 12 VDC-0.2 A power supply. According to the datasheet of the AL17150: “The AL17150-10B is a universal high-voltage input ...
    .. you hear the transformerless supply term, you initially imagine the capacitor-based solution: a high-voltage non-polarized capacitor in series ...
    Feb 12, 2026
25. Classic constant current cascode
    Stephen Woodward
    Circuits Measurement Supply Texas Instruments TL431
    .. quite well. One issue I found was that the output impedance (di/dv) was quite low; there was a change of 40 µA over a supply swing of 20 V (if I remember correctly), not linear with supply voltage change. It is possibly due to the 2.5 ...
    Feb 5, 2026
26. Short push, long push for sequential operation of multiple power supplies
    Jayapal Ramalingam
    Circuits Supply Microcontrollers Usage Microchip ATmega328P
    .. at 5 VDC, analog circuits operate generally at either 12 or 15 VDC. In some systems, it may be necessary to switch on power supplies in sequence, first 5 VDC to digital circuits and then 15 VDC to analog circuits. During switch-off, ...
    .. then 15 VDC to analog circuits after a preset delay. When you push the button SW1 for a long time, say 2 seconds, the 15-V supply is withdrawn first, and then the 5-V supply. Hence, one push button does both (sequential) ON and OFF ...
    Feb 4, 2026
27. Circuit controls inrush current in ac-operated power supplies
    Peter Demchenko
    Circuits Supply Power ON Semiconductor MOC3062M
    .. power supplies that operate from ac wall voltage have large input-filter capacitors. You must limit the inrush ...
    .. ac wall voltage have large input-filter capacitors. You must limit the inrush current to those capacitors. Otherwise, the supply may trip the ac circuit breaker, or you may damage the rectifier, filer chokes, or PCB ...
    Jan 30, 2026
28. Optically isolated overcurrent detector works from ac mains
    Jaime Castelló José María Espí Marcos Arasa Rafael García-Gil
    Circuits Measurement Supply Vishay 4N25
    .. Idea detects short-circuit faults or excess-current conditions in line-operated equipment, such as a UPS (uninterruptible power supply), across an isolation boundary. If the load current rises higher than a predetermined level, the circuit ...
    Jan 30, 2026
29. 5 octave linear(ish)-in-pitch power VCO
    Stephen Woodward
    Circuits Oscillators Microchip MCP602x
    .. months back, frequent DI contributor Nick Cornford showed us some clever circuits using the TDA7052A audio amplifier as a power oscillator. His designs also demonstrate the utility of the 7052’s nifty DC antilog gain control input: ...
    Jan 30, 2026
30. FM receiver/radio using Arduino and TEA5767
    Hesam Moshiri
    Circuits Arduino Microcontrollers Usage Radio TSC TS2937 TS2940
    .. chip. This chip is a 3 W+3 W Hi-Fi Class-D amplifier that can operate with only a single 5 V supply. The maximum output power can be achieved using 4-ohm speakers. According to the datasheet: “The PAM8403 is a 3 W, class-D audio ...
    .. tasks are performed by the Arduino-Nano code. R3, C7, C8, and C9 build a first-order low pass RC filter that reduces the supply noise. R1 and R2 are mandatory pull-up resistors for the I 2 C bus and CON1 is a UFL connector that provides ...
    Jan 22, 2026

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