Abstract: A test voltage is applied through an array of "guarded" switches (58) to selected ones of a plurality of components to be measured. Each switch (58) comprises first and second input terminals (69, 72), first and second output terminals (70, 74), and a wire (76) interconnecting the second input and second output terminals (72, 74). The switch (58) is operable selectively in a first state interconnecting its first input and output terminals (69, 70) and in a second state interconnecting the second input and output terminals (72, 74). A buffer amplifier (88) couples the input signal from the first input terminal (69) to the wire (76) interconnecting the second and output terminals (72, 74) of the switch (58) as a "guard voltage" to prevent loading of the input signal by leakage resistances within the switch.

Abstract: An amplifier circuit including provision for detecting non-linear circuit operation caused by the application of input signals that exceed either the amplifier dynamic range or the amplifier slewing capability is disclosed. The amplifier circuit includes the cascaded combination of a voltage amplifier stage, a voltage-to-current converter stage, a current limiter stage and an output stage. A first signal, obtained at the junction between a capacitor and resistor that are series connected between the signal common or ground potential and the input terminal to the output stage, is compared with a second signal obtained at the input terminal of the voltage to current converter stage. When the amplifier circuit is operating within the linear region these two signals are of equal magnitude or exhibit some other known relationship to one another.