The Tektronix 178 is a linear IC test fixture for use with the 577 Curve Tracer System. Test cards define the measurement function. Tests single, dual, or quad operational amplifiers, comparators, differential amplifiers, regulators and more. The 178 Curve Tracer Adapter is a linear IC test fixture for use with the 577 Curve Tracer System. Test cards define the measurement function. Tests single, dual, or quad operational amplifiers, comparators, differential amplifiers, regulators and more.