Column: Circuit drill
The performance of a voltage-to-current converter at low frequencies
By Dr Sulaiman Algharbi Alsayed, Managing Director, Smart PCB Solutions
triggers the circuit to produce a proportional output current via the load resistor (Rload
A ). These circuits have a wide range
of applications in consumer and industrial electronics, one of the most common being as a signal transmitter. There, parameters like pressure, temperature and others are transmitted to central control rooms, used to eliminate any voltage drops that might occur along the wires from the measuring instruments. In control applications, voltage-to-
current converter circuits may be used to provide a compensation feedback. One example is in active rectifiers, where the output current is adjusted to be proportional to the voltage being checked. This compensation loop contributes to the active rectifier’s ability to provide a steady output. However, there’s a question: Given
that the voltage-to-current converter circuit is intended to manage an alternating input signal, does it maintain a stable and satisfactory performance at low input frequencies? It is essential for any electronics designer to know this before applying this circuit in an application.
voltage-to-current converter (Figure 1) transforms voltage into a corresponding current. The input voltage (Vinput
)
Figure 1: A typical voltage-to-current converter circuit
Methodology To get an answer to our question, we set up an experiment, supplying the circuit of Figure 1 with 1Vac. We’ll vary the signal’s frequency between 1Hz and 200Hz, in 1Hz increments, all the while measuring the peak-to-peak amplitude of the output signal, and chart the results. For the experiment we assumed
the following: • The input signal is kept fixed at 1V (peak-to-peak) throughout the experiment.
• All circuit component values remained unchanged.
• Te temperature is kept at an ambient 25o 10 July/August 2023
www.electronicsworld.co.uk C. The relationship between the output
peak-to-peak signal and the input signal’s frequency is seen in Figure 2. The circuit achieves frequency stability at input frequencies over 75Hz. Another stable zone is noticed between 24Hz and 50Hz; however, the output’s amplitude drops in this zone, to roughly half the input signal’s. In addition, the performance of the circuit is poor when the input frequency range is between 50Hz and 75Hz, as well as below 24Hz. To prevent any distortion in the
produced signals, engineers must consider the voltage-to-current circuit’s stable performance zone for the application.
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 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60
