Circuits & Schematics: power supply - 10

91. LM4041 voltage regulator impersonates precision current source
    Stephen Woodward
    Circuits Supply Analog Devices LM4041
    .. current source of: It also illustrates how adding a booster transistor Q1 can accommodate applications needing current or power beyond Z1’s modest limits. Notice that Z1’s accuracy will be unimpaired because, with whatever ...
    Apr 27, 2025

92. Current monitor
    Peter Demchenko
    Circuits Measurement Supply Fairchild BC560
    .. every wall power supply has no indicator showing whether current is consumed by the load or not. It seems that this was a ...
    Apr 24, 2025
93. Simple logic probe uses bicolor LED
    Mark Shill
    Circuits Measurement Texas Instruments OPA2340
    .. 1B is which makes V LED = V B 2.5 V. The values of R 6 , R 7 , and R 8 are such that V B limits at the positive or negative power-supply rail when V PROBE is at the logic family’s minimum low or high level, respectively. Figure 2 shows ...
    .. the red and green LEDs are 2 and 2.1 V, respectively. Op amp IC 1A derives a buffered 2.5 V reference output from the 5 V supply, and R 3 limits the current to the LED when it is on. IC 1B buffers and amplifies the probed logic signal to ...
    Apr 23, 2025
94. Reduce EMI by sweeping a power supply's frequency
    John Betten
    Circuits Supply Texas Instruments TL331 UCC3813N-0
    .. power supplies can be notorious noise generators. You should prevent this noise, which is conducted, radiated, or ...
    .. effectively lowers the peak emissions. Figure 1. A low-frequency oscillator ramp, injected into the RC pin, modulates the supply’s switching frequency. The circuit in Figure 1 is a self-starting oscillator with an oscillation ...
    Apr 22, 2025
95. A negative current source with PWM input and LM337 output
    Stephen Woodward
    Circuits Analogue Design Supply ON Semiconductor LM337
    .. reverse bias of the load; some loads might not tolerate this. The 1N4001s block that, and also provide bias for the power-down cutoff of I OUT when +5-V rail shuts down. Note that the accuracy of I C R C = V ADJ is assured by the ...
    .. grounded load negative current source with a novel LM337 topology. With this topology, accuracy is insensitive to supply rail tolerance. The asterisked resistors are 1% or better and R S = 1.25 Ω. The PWM frequency, F PWM , is ...
    Apr 18, 2025
96. Water-leak detector uses 9V batteries
    Yongping Xia
    Circuits Measurement Analog Devices MAX934
    .. for many applications. This Design Idea describes a portable water-leak detector that uses a common 9 V battery for power (Figure 1). The circuit consumes less than 10 uA during detection mode, and a 9 V alkaline battery has ...
    Apr 18, 2025
97. Digital potentiometers enable programmable biquadratic filter
    Deborah Mancuso Donald Schelle
    Circuits Signal Processing, Filters Maxim MAX437
    .. expensive, the biquad circuit of Figure 1 may be a cost-competitive solution. Many filter applications require higher supply voltages, bipolar operation, or both, so the single 5 V supply associated with most switched-capacitor ...
    Apr 17, 2025
98. PWM-programmed LM317 constant current source
    Stephen Woodward
    Circuits Supply Fairchild LM317
    .. heatsink! Also note that R S should be rated for a wattage of at least 1.252/R S . Then there’s the consideration of power up/down transients. When the system is first switched on and C 1 is sitting discharged, and the controller will ...
    Apr 16, 2025
99. Infrared (IR) receiver circuit minimizes power consumption
    David Lees Donald Schelle
    Circuits Microcontrollers Usage Fairchild FDN359AN FDS6679 QSE113
    .. infrared (IR) signals while conserving system power is difficult, and typically requires the inclusion of complex power-management routines in the firmware. You ...
    .. are present, it returns the circuit to standby mode by de-asserting the Hold line. The circuit draws less than 2 uA of supply current while in standby mode, and approximately 40 uA when active. The combined battery monitor and ...
    Apr 15, 2025
100. White-LED driver provides 64-step logarithmic dimming
     Will Hadden
     Circuits Supply Light Analog Devices MAX1573 MAX4480
     .. circuit of Figure 1 is designed for portable-power applications that require white LEDs with adjustable, logarithmic dimming levels. The circuit drives as many as ...
     Apr 14, 2025

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