Analog electronics – rectification, filtering and transistor amplification
Design & TechnologyElectronics & MicrocontrollersAges 17–18
Use it with your class: students open it from a link or a QR code, with no account needed.
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Three basic analog electronic circuits on one screen: half-wave rectification with a single diode, full-wave bridge rectification with four diodes, and a transistor amplifier stage. Graphs plot the sinusoidal input voltage and the rectified output voltage; drag the filter capacitor to see the DC output ripple smooth out, and drag the load resistor to see the ripple increase as the load current grows. In amplifier mode, increasing the gain or the input signal amplitude too far clips (distorts) the output signal.
Lesson: Analog electronic components and circuits: rectifier diodes, DC power-supply filter circuits, transistors and amplifier circuits
What it shows
A diode conducts in one direction only, so it turns an alternating voltage into a pulsating direct voltage. A half-wave rectifier passes one half of each cycle, giving an average of about 0.45·U₂ and ripple at the mains frequency; a four-diode bridge uses both halves, giving about 0.9·U₂ and ripple at twice the frequency. A filter capacitor charges near each peak and discharges through the load in between, so a larger capacitance or a smaller load current means less ripple. The transistor stage amplifies a small signal, inverted, but clips it once the output swing would exceed the supply.
How to use
Start in Half-wave mode, set Filter capacitance to 0 and read the average voltage and ripple, then raise the capacitance step by step. Switch to the bridge rectifier with the same settings and compare the ripple and its frequency. Lower Load resistance to draw more current and watch the ripple return. In Amplifier mode, raise Voltage gain (amplifier mode) or the input amplitude until the output is clipped, then reduce it again.
Parameters you can change
- Circuit Half-wave rectifier (1 diode), Bridge rectifier (4 diodes), Transistor amplifier
- Transformer secondary RMS voltage 6–24 V
- Filter capacitance 0–1000 µF
- Load resistance 100–2000 Ω
- Voltage gain (amplifier mode) 2–100 times
Questions to explore
- How does the ripple change when you switch from half-wave to bridge rectification with the same capacitor and load?
- Why does the ripple grow when the load resistance is reduced, even with the same filter capacitor?
- At what gain does the output start to clip, and why can the output swing not exceed the supply voltage?
