A four-diode full-wave bridge

Turn both halves of a wave upright

AC means Alternating Current: its direction alternates. DC means Direct Current: it keeps one direction, even when its size changes. A full-wave bridge uses four diodes, with two conducting in each half-cycle, to send both halves through the load in the same direction. Peak means the largest instantaneous value.

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EXPERIMENT BENCH

Change the circuit settings, predict the readings, then check a challenge. These are learning models, with the assumptions explained in each lesson.

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How it works

Only an isolated low-voltage source; never mains. Each conducting diode drops 0.7 V in this model. No smoothing capacitor: the output is pulsating DC. This is not a tested hardware design.

Output peak = max(input peak − 1.4 V, 0). Two conducting diodes account for 1.4 V. The average current is the waveform average divided by load resistance. The output pulse repetition frequency is twice the input frequency. The doubled repetition applies only while output pulses exist. At input peak ≤ 1.4 V the bridge never conducts, and the repetition meter reads 0 Hz.

Difficulty

Build · Observe
Power on at input peak 5 V, input frequency 50 Hz and load 1 kΩ. Read output peak 3.6 V and repetition 100 Hz.
Need a hint?
5 V peak; 50 Hz; 1 kΩ → 3.6 V peak; 100 Hz
Explore · Adjust
At input peak 5 V and input frequency 60 Hz, keep average load current 1.8–2.0 mA.
Need a hint?
5 V peak; 60 Hz; 1 kΩ → about 1.909 mA
Solve it · Discover the limit
At input peak 9 V and input frequency 50 Hz, obtain average load current 8–9 mA.
Need a hint?
9 V peak; 50 Hz; 500 Ω → about 8.798 mA

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