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Utilise audio amps for voltage splitting (Part 3)

Posted: 16 Apr 2014 ?? ?Print Version ?Bookmark and Share

Keywords:voltage splitters? power audio amplifiers? PAA? op amps? transistors?

The dual switch S1A+S1B is for selecting two options: In position 1 we have two independent voltage splitters and the output voltages are adjusted with P1 and P2. In position 2 we have a single voltage splitter with four paralleled OAs and the output voltage is adjusted with P1. In the VS we may use a lot of ICs starting with low-cost OAs like the LM324 and TL084 or using the more expensive OPA4132, OPA4134, etc.

Voltage splitters based on DC amplifiers and motor drivers
Modern industry offers ICs specially designed to work as power operational amplifiers, e.g., the L165. The L165 is similar to the TDA2030, TDA2040 and TDA2050, and to some degree the LM1875. It is a special type of operational amplifier designed to work in power supplies and servo applications compensated for gain above 10 (20dB). Figure 15 gives the circuit diagram of a VS based around an L165.

Figure 15: A VS based around an L165 power operational amplifier.

The output voltage is adjusted with the trimmer potentiometer P1. The input of the IC is protected with C1, R3, D1 and D2. The gain of the IC is adjusted with R5 and R4 and should be above 10.

Voltage splitter with amplifiers and voltage regulators
We may use PAA and voltage regulators in the same VS and obtain additional regulated output voltages around the virtual ground of the output. Figure 16 gives the simplified circuit diagram of a VS built around PAA IC3.

Figure 16: Simplified circuit diagram of a VS built around a PAA, an LM317 and an LM337.

The output voltages V1 and -V2 depend on the PAA. The additional output voltages V3 and -V4 are produced by an LM317T and LM337T. Output voltage V3 is adjusted with P1 and -V4 is adjusted with P2. The circuit around IC3 is not given with all details.

Voltage splitters based on power and high-voltage operational amplifiers
Modern industry offers OAs with power supply voltages above 22V and with guaranteed output current above 15mA. Also there are OAs with significant power dissipation capability. These OAs are sometimes called high-voltage OAs (HVOAs), high-current OAs (HCOAs) or high-power OAs (HPOAs). Some of these OAs are appropriate for VSs and we should mention them because they extend the field of the applications of the VSs.

Table 2 gives some examples from the series OPAxxx produced by Burr-Brown/Texas Instruments. The circuits with classical OAs and PAAs with differential inputs mentioned above in the article are applicable to these OAs. In that case, a slight redesign of the presented circuit of the VS is needed and we will not discuss them again. We will mention that many of theses HVOAs and HPOAs can be used in voltage splitters from 36V and 48V batteries and DC power supplies.

About the author
Petre Petrov has worked as a researcher and assistant professor in the Technical University of Sofia (Sofia, Bulgaria) and as a lecturer and expert lecturer in Morocco. Now he is working as electronics engineer in Bulgaria.

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