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Interactive reference circuit schematics

Reference circuits with interactive component inspection, design formulas, BOM tables and an editable copy in Web CAD.

21 reference circuits

  • NE555 Astable Square Wave Generator

    7 components · 4 formulas
    Complexity: Basic
    Supply: 4.5 V – 16 V DC (Texas Instruments NE555; shown circuit uses +5 V)

    Standard astable relaxation oscillator topology outputting continuous square wave clock pulses with adjustable duty cycle.

    Timing & Oscillators

  • NE555 Monostable Delay Timer (One-Shot)

    7 components · 2 formulas
    Complexity: Basic
    Supply: 4.5 V – 16 V (TI §7.3)

    The one-shot circuit from the TI NE555 datasheet: press START and the output stays high for a fixed time set by one resistor and one capacitor, about 1.1 s with 100 kΩ and 10 µF.

    Timing & Oscillators

  • LM7805 5V Linear Regulator with Decoupling (L7805CV)

    8 components · 3 formulas
    Complexity: Basic
    Output: 4.75–5.25V at VIN=7–18V, IOUT=5mA–1A, TJ=0–125°C (ST Table 10)

    A nominal 9V-to-5V supply using ST L7805CV, input/output bypass capacitors, a discharge-path diode and an LED indicator. Includes conditional ratings and thermal calculations.

    Power & Supplies

  • BJT Astable Multivibrator & Dual LED Flasher

    10 components · 3 formulas
    Complexity: Basic
    Supply: 5.0 V DC nominal design assumption for educational demonstration. Requires sufficient headroom above the blue LED forward voltage (~3.3 V typ) to bias collector and base resistors; reverse base-emitter transients must remain within the transistor's absolute maximum rating (VEBO = 6.0 V for 2N3904BU).

    Discrete two-transistor cross-coupled relaxation oscillator driving alternating LEDs without an integrated circuit.

    Timing & Oscillators

  • LM386 Audio Amplifier with Gain 20

    7 components · 3 formulas
    Complexity: Basic
    Supply: 9V battery as drawn; LM386N-1 operating range 4 V – 12 V (TI §6.5); design table 5 V – 12 V (TI Table 9-1)

    The minimum-parts speaker amplifier from the TI LM386 datasheet: a volume potentiometer, the LM386 at its internal gain of 20, an output capacitor and an RC network driving an 8 Ω speaker from a 9 V battery.

    Audio Amplifiers

  • LM386 Audio Amplifier with Bass Boost

    9 components · 3 formulas
    Complexity: Basic
    Supply: 9 V battery as drawn; 5 V to 12 V design range (TI Table 9-5)

    TI Figure 9-9 redrawn as an editable LM386 bass-boost amplifier: a 10 kΩ and 33 nF feedback branch, volume control and an 8 Ω speaker powered from a 9 V battery.

    Audio Amplifiers

  • LM317 Adjustable Positive Linear Voltage Regulator

    6 components · 3 formulas
    Complexity: Basic
    Output: 1.25–9V respects recommended 3V headroom with nominal 12V input; regulation also requires the specified load, temperature and power conditions

    Adjustable DC voltage reference circuit using TI LM317KCS and nominal 12V input. Calculated setpoints up to 9V respect the recommended 3V headroom; usable current requires a load and thermal budget.

    Power & Supplies

  • LM317 Constant Current Source

    3 components · 3 formulas
    Complexity: Basic
    Input: 12 V selected; load voltage and regulator headroom must fit within it

    ST LM317T current regulator with a 12.4 Ω sense resistor for about 100 mA, 12 V nominal input and an input bypass capacitor. The external load connects between IOUT and GND.

    Power & Supplies

  • ESP32 Auto-Reset & Boot Flashing Circuit

    8 components · 3 formulas
    Complexity: Basic
    Logic: 3.3 V (VDD33 on the DevKitC V4)

    Dual-transistor auto-download circuit driving ESP32 EN and IO0 boot strapping pins via USB-to-UART DTR and RTS lines.

    MCU Interfaces

  • ±15 V Tracking Dual Supply (LM7815 / LM7915)

    14 components · 3 formulas
    Complexity: Advanced
    Output: +15 V and −15 V, tracking; up to 1 A (TI Figure 8)

    The ±15 V, 1 A tracking regulator from the TI LM79xx datasheet: an LM7915 trimmed to exactly −15 V and an LM7815 whose ground pin is driven by an LM307 op-amp, so the positive rail mirrors the negative one.

    Power & Supplies

  • TL431 Precision Shunt Voltage Reference

    5 components · 3 formulas
    Complexity: Basic
    Input: 10 V nominal (operates from 8 V to 15 V with appropriate R3 sizing)

    Texas Instruments TL431 programmable precision shunt voltage reference circuit producing 5.0 V nominal from a 10 V rail with a 470 Ω bias resistor and 10 kΩ / 10 kΩ divider.

    Power & Supplies

  • LM358 Inverting Operational Amplifier

    3 components · 3 formulas
    Complexity: Basic
    Supply: ±12 V split supply (operates from ±1.5 V to ±16 V)

    Single-channel inverting amplifier using the Texas Instruments LM358 dual op-amp providing -3.6 V/V closed-loop gain from a ±12 V split supply.

    Analog Sensing

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