Column: Circuit drill
The frequency operating window of an op-amp-based half-wave rectifier
By Sulaiman Algharbi Alsayed, Managing Director, Smart PCB Solutions T
he half-wave rectifier circuit is essential to most AC-to- DC converters. Tis circuit can be based on op-amps or conventional rectifiers, with the op-amp-based one
being more popular due to the benefits it offers. One such advantage is that it provides reasonable over-voltage protection, so in case of a failure, the downstream-connected part of the circuit will not see a highly- damaging current, unlike conventional rectifier circuits, which are usually very vulnerable to passing high currents. Figure 1 shows one popular op-amp-
based half-wave rectifier circuit, consisting of a single op-amp and a diode bridge, with its output shown in Figure 2. Tis circuit can be used in many applications, but an important question is, what frequency operating window can we use it with?
Experiment methodology We connect the op-amp-based half-wave rectifier circuit to a function generator with a sinusoidal output. Te input signal’s frequency changes gradually, at fixed intervals from 1Hz to 2MHz – there’s no need to go any higher. Te values of the input frequencies
and output amplitudes are measured and tabulated accordingly, to determine the relationship between the two. Te experiment was conducted
assuming the following: • Te input signal amplitude was kept constant at 1Vac;
• Te input signal DC offset was kept at 0Vdc;
• Te op-amp supply circuit is kept stable;
• R1, R2, R3, D1, D2 and the op-amp were leſt unchanged;
• Te power supply voltage was kept constant, to avoid interfering with the collected data;
• Te circuit’s output was not connected to any load, to focus on studying the two variables: input frequency and output amplitude; see their relationship in Figure 3. From the curve in Figure 3 we
conclude that the half-wave rectifier circuit operates better at lower frequencies. Te higher the input frequency, the lower the output amplitude. Another observation is that
the relationship between the two parameters is exponential, showing that the output signal amplitude deteriorates severely when the circuit operates at higher frequencies.
Figure 1: Typical op-amp-based half-wave rectifier circuit 10 February 2023
www.electronicsworld.co.uk
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48
