Circuits & Schematics Fairchild - 2

11. Self-oscillating H bridge lights white LED from one cell
    Luca Bruno
    Circuits Oscillators Supply Light Fairchild BC550 BC557
    You can build a self-oscillating H bridge by replacing the pullup collector resistors of a classical BJT (bipolar-junction-transistor) astable multivibrator with PNP BJTs (Figure 1). Because this circuit oscillates at supply voltages as low as 0.6 ...
    Feb 15, 2023
12. DC/DC converter using transistors
    Mithun K. Das
    Circuits Beginners Supply Fairchild BC547
    Sometimes, you may need to make a DC/DC converter with minor components that can handle small loads. In this article, we are going to make something like that. This DC/DC converter using transistor has only a few components and can handle small ...
    Jan 12, 2023

13. Astable multivibrator lights LED from a single cell
    Luca Bruno
    Circuits Supply Light Fairchild BC550C
    Lighting LEDs from a single 1.5 V cell poses a problem because their forward voltages are higher than the cell’s. The simplest way to light the LED is to use a step-up dc/dc converter. This Design Idea offers a simple and reliable alternative ...
    Dec 23, 2022
14. Circuit adds foldback-current protection
    José María Espí Rafael García-Gil
    Circuits Supply Fairchild LM317
    For many applications that require power-supply currents of a few amperes or less, three-terminal adjustable-output linear voltage regulators, such as LM317 , offer ease of use, low cost, and full on-chip overload protection. The addition of a few ...
    Nov 5, 2021
15. Position detectors provide motor-control logic
    Steve Pomeroy Russell Hedges
    Circuits Power Fairchild H21B1
    In the circuit of Figure 1, assume that a brush-type dc motor must drive a load back and forth between two endpoints on a lead screw. Optical sensors determine end of travel, and an SPDT switch selects to which end to send the load. The sensors ...
    Sep 21, 2021
16. A discrete auto power-off timer with excellent characteristics
    Patrick Van Torre
    Circuits Supply Fairchild BC547
    Over the years, various power-off circuits have been published. However, the circuit proposed here is very simple and has excellent characteristics. It features a fast power-off transition, with only 8 mV voltage drop at power on and sub-µA ...
    Sep 7, 2021
17. Two transistors form high-precision, ac-mains ZCD
    Circuits Analogue Design Fairchild BC549B
    Many applications that use 110 V/230 V-ac mains require a ZCD (zero-crossing-detection) circuit for the ac-line voltage, for example, to synchronize the switching of loads. One method of ZCD uses a high-value current-limiting resistor or a ...
    Jul 1, 2021
18. Circuit controls intensity of reflex optical sights
    Stephen Woodward
    Circuits Automation Games Light Fairchild L14Q1
    A popular category of aiming/pointing aids is the reflex, or “red-dot,” sight. This system finds use in such diverse applications as astronomy, archery, and shooting. In the reflex sight, light from an internal source typically a ...
    Mar 3, 2021
19. Voltage-to-Current Converter Drives White LEDs
    Susanne Nell
    Circuits Supply Light Fairchild BC548C BC558C
    You sometimes need to drive a white LED from one 1.5 V battery. Unfortunately, the forward voltage of a white LED is 3 to 4 V. So, you would need a dc/dc converter to drive the LED from one battery. Using the simple circuit in Figure 1, you can ...
    Feb 12, 2021
20. Pocket white-LED torch is power efficient
    Circuits Supply Light Fairchild BC559
    This Design Idea describes a single white-LED torch, which can be housed in an empty glue-stick tube and has a long rechargeable-battery life. The circuit is constructed with just a few commonly available parts. This torch has proven to be highly ...
    Nov 3, 2020

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