Abstract:

The operational amplifier (opamp) is a ubiquitous building block in analog electronic systems. It can be found in different amplifying configurations, including instrumentation amplifiers, active filters, data converters, etc. Often the specifications required to the opamp are very demanding and huge efforts have to be devoted to its design. Furthermore, the performance must be confirmed experimentally, requiring the use of multiple testbenches in order to establish open-loop or closed-loop arrangements that lead to the extraction of the measured parameters.

The opamp is studied in electronic engineering degrees from the basic courses up to the most specialized subjects. This study comprises the theoretical behavior of the circuit, as well as practical aspects as its design, simulation, and test. Indeed, it is very common to carry out labs in which circuits with opamps are implemented, regardless of the degree of abstraction used to consider this block.

There are labs in which the main purpose is to assembly a circuit including one or several operational amplifiers. Nevertheless, in advanced courses it is usual that the emphasis must be put on the measurement procedure and in the interpretation of the results. In these cases, having a board in which the operational amplifier is pre-connected according to the intended configuration results in an important saving of time that can be devoted to set up the measurements and acquiring, representing, and discussing the data.

A reconfigurable prototype, built on a printed circuit board (PCB) support and suitable to connect an operational amplifier in different configurations, is described in this paper. The proposal aims at facilitating the measurement of the most characteristic parameters of operational amplifiers with a dual-in-line (DIL) package and a number of pins between 8 and 48. This allows characterizing commercial components as well as full-custom ASICS, which are connected to the board by means of a zero insertion force socket. The PCB contains auxiliary components that allow the connection of the opamp in different inverting and non-inverting configurations. This way, parameters such as the offset voltage, the gain, the gain-bandwidth product, the slew rate, the input and output voltage range, the CMRR or the PSRR, among others, can be measured.

The block diagram of the prototype is described and the different reconfigurations of the board required for each type of measurement are detailed. Besides, the design and implementation of the PCB is reported. Finally, some selected experimental responses obtained from a LM324 opamp by using the proposed solution are illustrated. The results obtained during the characterization of the prototype confirm its suitability to be used in the labs of different subjects related to analog electronics of the Bachelor Degree in Electronic and Automation Engineering of the University of Extremadura (Spain).

Keywords:

Electronics labs, experimental characterization, operational amplifier, parameters extraction, printed circuit board, reconfigurable.