By choosing from a complete list of active and passive components, including resistors, capacitors, inductors, diodes, transistors, MOSFETs, ac and dc voltage and current sources, users of ProtoLab 4.0 can create and analyze circuits instantly on a PC. The new circuit design and simulation package also allows users to select from an extensive library of pre-designed circuits that can be edited instantly to save time when designing circuits. After completion of the desired circuit, users can analyze the circuits accurately by utilizing a complete range of virtual test instruments, including a voltmeter, ohmmeter, ammeter, wattmeters, and oscilloscope. The package is for use with IBM PC-386 or higher.